Nielsen Online reported today that Twitter enjoyed a doubling in its user base last month, March 2009. And April will be even wilder, I suspect, with all the attention (read: hype) that celebrities like Ashton Kutcher*, Mrs. Kutcher (Demi Moore) and Oprah brought to the medium. Will the success last, though?What’s the problem?

The retention rates are still abysmal [this means "immeasurably low" according to Merriam Webster; OK, it's maybe not that bad]: only 40% of the new subscribers are still using the service ONE month later! The only silver lining is that it used to be even lower: 30%! David Martin, vp, primary research, Nielsen Online, sees this as thunderclouds hovering over Twitter’s head (head? Ah well… the virtues of having English as a second language, eh?)

Read the article about this research here.

* Ashton Kutcher had a Twitter challenge to get 1,000,000 followers (he was the first one to surpass that landmark). Demi Moore’s Tweets stopped someone from committing suicide (the story on CNN), and Oprah has carefully started Tweeting on April 17th.

Click here to view the embedded video.