Reports from Neilsen Media Research announced in March that Twitter, the social networking and micro-blogging service that enables its users to send and read other users' updates, has seen a U.S. user growth of 1,382% between February 2008 and February 2009.
Read which other social media tools are making an impact in Caroline McCarthy's "The Social" article: Neilsen: Twitter's growing really, really, really, really, really fast
