@BloodDonorsIn - a story of how the power of Twitter's 20 mln population across various parts of India was harnessed to build a community focussed on matching blood donors with patients in need, a vital social need. This is a rare many-many community on Twitter, with an anonymous founder and around 170K members. A real-time empathy network, @BloodDonorsIn is a community on the lines of Lennon's Imagine,with strangers unconditionally helping others across boundaries of religion, ethnicity, language etc.