BOSTON ( MainStreet) -- For as long as there have been celebrities, there have been celebrity endorsements. Milton Berle introduced America to the mighty men of Texaco (working pumps from "Maine to Mexico"). Mean Joe Greene's spot for Coca-Cola ( KO) is considered a classic. O.J. Simpson dashed through airports for Hertz ( HTZ) long before he made a run for the border in a white Bronco. Using celebrities has been an effective tool for advertising and marketing efforts. Though perhaps naively so, consumers have tended to trust these familiar faces and transfer likability to things associated with them. In recent years, however, celebrity endorsements have become even more manipulative and, one could argue, sleazy. When it comes to taking shopping or financial cues from the rich and famous, buyer beware. The Federal Trade Commission cracked down on "mommy bloggers" who failed to disclose the free swag they collected for their glowing reviews. But, despite general guidelines for what crosses the line, celebrity tweets haven't been nearly as scrutinized by that agency or other official watchdogs. When 50 Cent hyped a headphone company, H&H Imports, on Twitter, what his 3.8 million followers didn't know is that it had more to do with his stock portfolio than the product. The penny stock's price spike earned him nearly $10 million, on paper at least. The Kardashian clan's Twitter feed is a steady stream of paid-for name dropping. Ashton Kutcher has been in hot water twice because of his promotional acumen. CBS slapped him on the wrist (ever so gently) when logo stickers for tech companies he invests in were stuck on a laptop and thereby prominent throughout a scene on his sitcom Two and a Half Men. When Details magazine had him "guest edit" an issue, he used the opportunity to pimp some of those same companies -- among them FlipBoard and Foursquare. The FTC was prompted to issue a statement (a tweet, actually) to tell critics they had no intention of looking into the matter. Sleazy, by definition, describes an endorsement deal made by pop star Ke$ha: For her "Get Sleazy" tour, she inked a deal with LifeStyles Condoms and the company went so far as to make a promotional line with her face on the wrapper (something that, with apologies to Woody Allen, might help more than thinking about baseball). Bob Eubanks, who used to host the The Newlywed Game, was in an pickle back in the '90s when his paid testimonial for a 900-number dating service was used to help bilk millions from investors (he was never blamed directly by investigators). Cybill Shepherd heeded the advice "take the money and run" when she took a paid gig as spokeswoman for the Beef Industry Council in 1987. It was later revealed that she was actually a vegetarian.