"The next time an overly friendly blond sidles up in a crowded bar and asks you to order her a brand-name martini, or a cheery tourist couple wonder whether you can take their picture with their sleek new camera-in-a-cell phone, you might want to think twice," warns Daniel Eisenberg. "There's a decent chance that these strangers are pitchmen in disguise, paid to oh-so-subtly pique your interest in their product." Eisenberg examines the growing use of "stealth marketing" -- covert product placements. No longer content to place their products on TV shows and movies, marketers are planting shills in bars, restaurants and other places, blurring the line between advertising and real life.