Ideas

• Create a PledgeBank pledge, then let your social network know how to help collectively raise money for a cause ("I will give $X dollars for Y cause, but only if N number of others will do the same") -- good example of positive peer pressure
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Articles 

• To Nonprofits Seeking Cash, Facebook App Isn't So Green: Though Popular, 'Causes' Ineffective for Fundraising NYTimes 4/24/09
  • Response to article: Now Washington Post Dissess Bloggers