"There's a big overlap between cultural and business and charitable networks," the attorney said. "You'd need to be a sociologist or archaeologist to graph out these relationships."
There could be unseen benefits for the celebrities, business leaders and companies that contribute to charity events, notes Newman. The entertainer who offers to perform at a gala could do so, in part, to gain favor with the organizer's spouse, with whom he does business. Or a Hollywood agent may support a studio head's charity, then later ask for an audition for an actor he represents.
"A lot of these charities hire celebrities to endorse them," said Borochoff. "And they can hide it."
Businesses and individuals can also boost their own images by aligning with charitable efforts. Angelina Jolie went from wild child to global do-gooder by lending her support and her famous name to humanitarian causes, notes Dorie Clark, a marketing and branding consultant. And celebrities might join forces with charities to "give the media something to talk about ... rather than gossip about their love life," she said.
Another reason celebrities like associating with nonprofit groups aiming to better the world?
"It's a way for them to prove they're smart and they're serious in an industry known for its vapidity," Clark said.
Companies that support charity galas by shelling out for expensive tables can appear to be good corporate citizens, she said, and it also allows their executives to mix and mingle with celebrities and other influential trendsetters.
"The networking benefits are great and the publicity benefits are great," she said.
The charities need the stars, too, both for publicity and brand association.
"Celebrities can grab attention like nobody else," said Tim Saunders, features editor at LooktotheStars.org, a website that chronicles celebrity charity news. "If you have a celebrity attached to your gala, you have instant publicity."