The study, which scored 87 celebrities and sports figures who have appeared in an ad in the last year, focused on overall awareness and whether a celebrity left a positive impression in consumers' minds. With all the celebrity endorsers these days, it's a bit of a surprise that none of those mentioned above are considered A-listers or command top ad rates. (Catherine Zeta-Jones reportedly pocketed the most expensive celebrity endorsement last year for her $20 million, two-year deal with T-Mobile, according to trade pub AdWeek.)

The results suggest there's a big difference between remembering a person and buying something from them. Some of the most exposed celebrities, for instance, had the most negative effect on buying habits. Sexpot Anna Nicole Smith, hotel heiress Paris Hilton, pop tart Britney Spears, supermodel Kate Moss and real estate mogul Donald Trump were all examples of celebs whose association made it less likely a person would buy a product, the study said.