Despite being among the more lucrative Facebook applications, (Lil) Green Patch accounts for less than 3% of The Nature Conservancy's online fundraising — which itself generates just 10% of all individual donations to the group, Citro said.
Yet the conservancy is less concerned with raising big bucks than with planting seeds for future support from the younger generation active on social networks.
"It's really a great branding tool," Citro said. "It's helping spread the word, educating people about our organization and its mission."
The group recommends its social-networking activities to past donors who cannot afford to give cash because of the bad economy but still want to help, she said.
Even if social-networking sites draw relatively little money now, it's imperative for nonprofits to explore them, said Melissa Brown, associate director of research for the Center on Philanthropy at Indiana University.
Surveys by the center show that direct mail and phone solicitation have become less successful in recent years, while Internet fundraising has risen steadily. As more users gravitate to social networks, it makes sense for nonprofit groups to follow.
"This is a time for experimenting with the social networking, figuring out how it can work for your organization," Brown said.
The Humane Society of the United States used a Facebook application to promote this year's "Spay Day" drive in support of spaying and neutering.
The campaign invited people to upload photos of their pets to a Humane Society website and solicit contributions from family, friends and others. A Facebook application — and other interactive "widgets," or small programs for blogs and MySpace pages — helped participants reach more potential donors.
The "Spay Day" drive raised $600,000 from about 40,000 participants, said Carie Lewis, the Humane Society's Internet marketing manager. It's uncertain how much was generated through Facebook. But this year's campaign, the first to use the application and other widgets, was more successful than previous ones. In 2008, the 31,000 participants raised only $72,000.
NCM Fathom Events, an entertainment company based in Centennial, Colo., sponsored a four-day fundraiser in March for the anti-poverty group CARE using another rapidly growing site, Twitter.
For every "tweet," or short message, supporting the campaign, Fathom Events made a pledge. The "tweet-a-thon" raised $5,000 for CARE, said Tobin, whose company promoted it.
Social-networking sites "lower the fundraising barrier," offering nonprofits an inexpensive way to reach mass audiences, Tobin said.
"Before, you had to have a budget for advertising space," he said. "What you need to have now is a really good idea that people gravitate toward. If you have that and make it fun or pull at the right heartstrings, you can get a lot of activity going."
One potential pitfall: "Donor fatigue" might set in as social-networking sites become increasingly cluttered with pleas for help from do-gooders, said Lee Rainie, director of the Pew Internet and American Life Project.
As people's time and wallets are stretched ever thinner, they could decide that installing an application is their "charitable good deed for the day," leaving them less inclined to write a check or volunteer at the soup kitchen, Rainie said.
"This is making the battle for people's contributions and charity endeavors and volunteer time all the more competitive and brutal," he said.
Marble, one of the (Lil) Green Patch players, said she appreciates that the game is simple to use and doesn't badger her to send cash. She just hopes the requests to swap plants don't get out of hand.
"If it gets too much, I might consider uninstalling or just clicking the 'ignore' button on all of them," she said. "But that hasn't happened yet, so I'm still playing."