A-List Angels

"When Ashton Kutcher first heard about 50 Cent's nine-figure Vitaminwater windfall in 2007, the actor realized he'd been missing out. He soon followed the rapper's formula--seeking equity instead of cash for endorsement deals--but with a twist: as the first person to top 1 million Twitter followers, Kutcher leveraged his social reach to accumulate stakes in a vast range of user-hungry tech startups. A decade later, Kutcher is perhaps the brightest in a firmament of star investors from Beyonce and Jay-Z to Jennifer Lopez and Alex Rodriguez. Bartering credibility and connections in exchange for…