Ever since Pope Leo XIII lent his image to the promoters of the drink Vin Mariani in the late 19th century, brand marketers have been striving to recreate the holy union of product and personality that fuels sales and gives a brand star quality. Nowadays, globally, about 20% of adverts include a celebrity; in Latin America and Asia, a quarter contain a famous face.

Yet the recession has brought with it a degree of fame fatigue. Consumers have shown they no longer want to be bombarded with images of glamorous lifestyles and the familiar faces of those who lead them. In these difficult economic times, it appears that glamour has quickly become suggestive of smugness. Weekly celebrity magazines in the US have been shedding sales, and titles such as Glamour and Vanity Fair have been replacing their Hollywood cover stars with little-known models and athletes; in Britain, celebrities are appearing in fewer ads than at any other time in the past 15 years. Market research company Millward Brown says that only 5% of ads in 2009 included a famous face (the figure was triple that at the turn of the century); in the US, about 9% feature a celebrity. Meanwhile, the unravelling of the Tiger Woods-as-family-man myth has given many brands pause for thought before signing up a celebrity.

Even so, despite the twin attacks of recession and scandal, the consumer pulling power of celebrity survives, and in some spheres it’s doing better than ever. A survey of consumers in 25 countries by media agency MEC MediaLab Global at the end of 2009 found that one in four admitted to buying something because of the celebrity promoting it; in Asia and Latin America, people were more than twice as likely to say a star’s endorsement influences their purchasing decisions. More than half of consumers said a celebrity helps a brand stand out, and nearly as many said they add to a brand’s personality, which rose to 60% for 20-and 30-somethings; 29% said a celebrity endorsement helps them trust a product.

Gary Cooper of Munich-based B-C-C, an agency linking brands with stars, says business has been booming as brands have sought to reassure consumers and maintain visibility during the recession by using celebrities: “We thought it was going to be a tough year, but we’ve never had as much work.” His recent deals include Justin Timberlake for Audi, and Michael Schumacher for an organic food range.

So, what about when the star behaves badly? Do celebrity indiscretions really hit a brand’s bottom line or damage the business of endorsement as a whole?

Damian Thompson, head of consumer insight at MEC MediaLab Global, says one-off, high-profile celebrity own-goals don’t largely damage brands or the appeal of using stars: “There are some that would like us to believe that the way brands use celebrities will have changed because of Tiger Woods; I don’t think it has.”

In fact, since the Woods story broke, several big-budget, star-studded global ad campaigns have been launched or announced. Sportspeople are hot property in particular, especially football players given that it’s a World Cup year. Louis Vuitton has launched a campaign featuring footballing legends Pele, Diego Maradona and Zinedine Zidane; Nike has used a host of international footballers for its three-minute World Cup advertising spectacular; and diamond company Steinmetz provided diamond-encrusted steering wheels and helmets for F1 drivers Lewis Hamilton and Jenson Button at the Monaco Grand Prix. Meanwhile, fitness brand Power Plate, which previously used TV personality Dannii Minogue and actress Courteney Cox, this year signed a deal with the Williams F1 team, as it hones its sports and fitness image, and searches for more male consumers.

Even Tiger Woods – who at one time was estimated to have earned $100m a year through endorsements – is still in demand. While he was dropped by AT&T, Gatorade and Accenture when news of his infidelities broke, games producer EA Sports says it saw no dip in sales of its Woods-fronted golf game, and has confirmed that Woods will be the face of PGA Tour 11. Nike, which also stuck with Woods, was reported to have seen a dip in sales of women’s footwear immediately after the story broke, but its share price has steadily risen since. The share prices of both Accenture and EA have been stable.

Millward Brown has found that while some celebrities help brands achieve prominence and memorability, ads with a celebrity are, on average, only slightly more enjoyable to consumers than those without, and are usually no more persuasive than ads with ordinary people.

“It’s certainly not a magic bullet to effective advertising.” says Dominic Twose, Millward Brown’s global head of knowledge management.

Hamish Pringle, director-general of the Institute for Practitioners of Advertising in the UK and author of the book Celebrity Sells, says ads have to be good as well as star-studded to be effective. “Celebrities are an excellent advertising device, but celebrity is not an idea in itself.”

Sometimes, however, the results are unarguable. For example, the relationship between Nike and basketballer Michael Jordan, carefully managed over 20 years, gave the brand huge credibility and turned the athletic shoe industry on its head. In the US, 30% of consumers questioned last year associated Jordan with Nike, and in Singapore, 42% linked him with Nike or Air Jordan shoes, a version of which is still launched every year, even though Jordan has long-since retired from sport.

Tiger Woods may, for some people, now be shorthand for endorsements gone bad, but he’s hardly been a disaster for Nike. “Nike started with a 1% share of the golf market and now has 15%,” says Pringle. “Most people would say Tiger Woods had something to do with that.” Similarly, when scandal-attracting supermodel Kate Moss became the face of Burberry, sales rose 25% in a three-month period.

Celebrities also breathed new life into Hewlett Packard, which was struggling in the PC market until rapper Jay-Z, snowboarder Shaun White, hip-hop artist Pharrell Williams, fashion designer Vera Wang and tennis star Serena Williams gave consumers a new side to the brand – and gave HP its old title of world number one PC brand. In China, Motorola’s The Tribe campaign, using stars noted for their confidence and personal style, including David Beckham and the designers Dolce & Gabbana, generated a significant increase in market share, and revenue of 15 yuan for every one spent on media.

To be infl uenced, Thompson says, consumers don’t have to believe the celebrity shops at the supermarket they’re endorsing, nor does the supermarket expect them to believe it. What matters, he says, is that it’s conceivable that the person might go there – that if they ran out of milk, that’s where they might head.

“We’ve known for a long time that consumers are completely savvy to all the games we play,” Thompson says. “People know full well these celebrities are being paid; they understand that. That said, many of the approaches we use still work.”

With this in mind, brands continue to court stars; but, just as consumers have grown more selective about the celebrities they want to see, so too have celebrities about the brands they’ll associate with – even if the money’s right. Gone are the days of Hollywood A-listers sloping off to Japan to endorse products they’d never heard of, in ads they hoped their fans at home would never see; the business of celebrity endorsement is morphing into a more subtle relationship – more a meeting of marketing minds, a brand symbiosis, than a simple sale to the highest bidder.

Cooper says celebrities now tend to want to partner brands that have strong corporate values and sustainability policies that reflect well on them. “They don’t want to endorse a gas-guzzling SUV,” he says. “That wasn’t the case two years ago, when it was just about which car was bigger.” Cooper is currently negotiating a car deal for the Black Eyed Peas, who have said they want to endorse a hybrid or electric model, while singer Pink only agreed to endorse the VW Polo because it was the most economical car VW had built.

Peter Hess, co-head of commercial endorsements at CAA, the LA-based international artists’ agency, whose clients include Brad Pitt, Oprah Winfrey and singer Shakira, says the discussions about whether a brand is right for a celebrity are not unlike the due diligence any business goes through before agreeing a partnership. “Generally speaking, people in the entertainment business are savvy and know what’s going on in the world,” he says. “They will always look to be at the forefront of an issue, whether political, social or economic, and … choose opportunities that are not going to have the effect of souring the support of fans.”

As Cooper says, the dynamic between products and stars has changed: it’s as much about chemistry as simply matching of a face with a name. “We’re in the middle of two brands,” he says. “You have to bring them together in a way that makes sense for them both, so they’re complementing each other, not fighting for attention.”