So George Clooney's throwing parties for Darfur. Brad Pitt's building green homes in Katrina-ravaged New Orleans. Angelina Jolie's tromping around the Third World as a United Nations goodwill ambassador.

Sure, these jaunts make for great photo-ops. And having a Hollywood heavyweight wax poetic about children in need, animals in danger, regions in crisis or another cause du jour is sure to elicit warm and fuzzy feelings in the people who care about celebrities and their causes.

But do fans actually follow in stars' philanthropic footsteps?

Studies about Americans' charitable giving habits and reports from those who work in philanthropy say that while a famous name can raise a cause's profile, it doesn't necessarily get people to open their wallets.

"It certainly benefits an organization to have a celebrity associated with them, because it raises the level of seriousness around the topic. But the charity has to be in a position to convince other people to make a commitment," said Lisa Pelofsky, CEO of Pelofsky and Associates, a company that provides fundraising services to nonprofits.

"I don't think people make a commitment to things just because the person they like the most is talking about it," she continued. "These kinds of decisions aren't made impulsively."

Indeed, it seems that when it comes to giving, an Academy Award winner may have less sway than a potential donor's mom and dad. A 2006 study done by Cone, a Boston-based company that helps charities conduct marketing, found that few people pick charities based on celebrity involvement.

Out of more than 1,000 adults surveyed, only 15 percent said they would donate to a cause because of its affiliation with a star. By contrast, 77 percent said they could be swayed to contribute on the advice of family members and 64 percent said they'd give on the advice of friends.

Celebs Woo Paparazzi, Not Necessairly Donors

Sandra Miniutti, vice president of marketing for nonprofit charity-rating firm Charity Navigator, said it's probably best that most Americans don't dole out donations based on a megawatt smile or marquee name.

"What we tell our donors is not to give to something just because it has a pretty celebrity face on it," Miniutti said. "You have to do your research."

Charity Navigator evaluates organizations based on their financial health, including what percentage of donations go to administrative costs. They rate charities on a zero to four-star rating scale, four-stars being the highest. Their rankings of celebrity-endorsed causes show that not all may be deserving of the everyday American's dollars. While Michael J. Fox's Foundation for Parkinson's Research rated four stars, Larry King's Cardiac Foundation only scored one.

Whether or not their involvement attracts more attention or money doesn't seem to have stopped celebrities from hooking up with causes as readily as they hook up with one another.

One of the latest and seemingly most absurd matchups is Backstreet Boys' Nick Carter and the dolphins. In May, the United Nations Environment Program Convention on Migratory Species appointed Carter the special ambassador of the Year of the Dolphin, making him the public face of the campaign to save the mammals.

A representative for the organization said that while Carter has yet to do anything for the dolphins, he'll soon start taping public service announcements about the sea creatures that share his vocal gifts. Carter also plans to put his Backstreet Boys-honed talents to use by recording a song in honor of the dolphins.

Pelofsky noted that in the end, whether it's a boy-band singer or A-list actress, most charities welcome the chance to sign on a celebrity: Even if they don't draw in a bigger donor base, the star power helps raise the nonprofit's profile. But there are certain pairings that would probably never work: Say, Lindsay Lohan and MADD or Britney Spears and

"Would I ever turn down a celebrity who's interested in helping a nonprofit? Not unless I was working for the Humane Society and it was Michael Vick," Pelofsky said.