As a sidenote to the horror in Mumbai, the inarguably important role that Twitter and other "nonprofessional" news sources has played in distributing news about the unfolding terror attacks will become a part of the ongoing debate about the future of journalism.
Contentious has a great round-up of social media coverage of the attacks.
Matthew Ingram looks at the credibility issue with Twitter and concludes that occasionally misleading information does not disqualify it as a good news source. (The gripe is that no one is fact checking Twitter. And of course they aren't.) For example, the news that Marriot in Mumbai was under attack came via Twitter, this turned out to be false, apparently. Ingram points out, though, that other Twitterers quickly corrected the misinformation.
The fact that this is even at issue astonishes me. Doesn't everyone know that what we call "facts" are subject to revision and to change, as time invariably brings more information and more context? (See: the earth is flat.) And in a breaking news enviroment, absolute truth is a standard that no medium, no journalist, could possibily live up to.