Hollywood's new triple threat: actor, singer, would-be tech mogul. Taking a page from the Ashton Kutcher handbook--the TV star runs his own digital-media company and helped fund Foursquare, Skype and Spotify--a new crop of A-listers is aiming to parlay their celebrity into smash-hit start-ups. In lieu of launching clothing lines or branding vodkas, they want the cachet, and the cash, of "becoming a serious tech investor," says Eli Portnoy, CEO of Orlando-based branding firm Culture Ranch.
That's a daunting challenge. Although celebrities excel at getting attention--budding investor Justin Bieber commands 25 million Twitter followers--business is a different game. For every Kutcher,...