I hate pledge drives. The thought of being contacted to give money to an organization, even one that I normally support, makes me uneasy. But I am happy to raise money for organizations I support and like the idea of competing against others towards a goal. To maximize their ability to raise money, organizations should use Micro-giving campaigns to supplant and eventually replace traditional pledge drives.
A successful micro-giving campaign should do the following: provide a limited time for action; allow me to set a reasonable goal that I can match; and give me a means to share my progress with others and link our goals toward a larger “big goal”. I think Tim Ferriss’s Tweet to Beat campaign is an excellent prototype for a product that companies like Convio could produce to allow existing organizations to take their campaigns and turbo-charge them through social media.
Tweet to Beat is interesting as an idea because it allows individuals to align themselves with the goals of an organization and to offer personalized “challenge grants”. I imagine that pledge drives don’t use these tools all that often for regular donors today because of the difficulty in administering the program. I’d be happy to give an extra $10 or $20 to an organization if I knew that my marginal $10 or $20 made a big difference in the number of donors that my organization of choice was able to attract. Offering this recognition for “helper donors” is a big key to the journey from a hated pledge drive call to an engaged donor base of people who not only care about a cause or an organization but are also able to easily and quickly provide support to that cause or organization.
Convio already offers a version of this service — currently used for events like the Tour De Cure bicycle fundraiser — but I wonder whether they’ve considered expanding it for events like a local public television fundraising drive. Or even if Convio has considered making this service available (perhaps through Twitter, perhaps through Facebook) so that any 501c(3) organization could have better tools to take advantage of the reach of social media.
Pledge drives exist today for organizations like Public Radio and other 501c(3) organizations because they are an effective means of engaging potential donors (or perhaps just making them feel guilty enough to give money to get someone off of the phone). These organizations are missing new potential donors who today might ignore email appeals from someone they don’t know but would be open to appeals from their friends to support causes those friends believe in and support. In the process, organizations can gain new tools for engagement and reach donor bases that are negative or do not respond to traditional fundraisers.
Information Maven 
Greg, thanks for the Convio mention. Actually, the tools are already in place to do something like Tweet to Beat. Simply replace the donation form, but do the rest as Tim has explained. As for the challenge aspect, this can be done as well. Convio has widgets that can be created in conjunction with any donation form, advocacy action alert, or special fundraising event. To create a wide network of helper donors, to use your term, the organization could simply put the opportunity to pick up the widget on the thank you page of their initial donation, encouraging them to post the widget on their social networks, email signature, anywhere they can paste HTML, and to also challenge their friends to donate/pick up a widget. The org could relatively easily post individual widget results in rank order to show who was doing the most, and of course, each widget shows how much the “owner” has done, so friends could easily see how they stack up just by visiting their friends’ profiles.