While the world is holding their breath in what turns out as the worst terrorist attack since 9/11, the Mumbai events have shown that grassroots journalism plays an increasing role in reporting quickly about non-localized, unfolding events. As summarized well by the Telegraph, online media have started to report, and update continually, about the tragic event in Mumbai. In particular Twitter is used to broadcast breaking news, and informing friends and relatives about what is happening in India. There are about 5 new tweeds (updates) per second. Vinu and others photorecords on Flickr.
These media probably won't change the world (and as the Telegraph writes, they might be used by the terrorists as well), but they create transparency and quick access to information.