In recent weeks it seems like every news outlet has been talking about the rapid growth of Twitter, but one expert says that if the microblogging service is to continue its ascent, it will need to keep new users from abandoning the site.

David Martin, vice president of primary research at Nielsen Online, says that although Twitter has seen dramatic growth over the last year, currently more than 60 percent of Twitter users stop visiting the service after a month. Before the recent media storm for the site, that number was closer to 70 percent.

Although Twitter is the new kid on the block, Martin says that the site’s retention rate is still less than half that of Facebook and MySpace when they were around the same age.

Martin writes that while the news that Oprah Winfrey, Ashton Kutcher and other celebrities use Twitter has grown its membership, to maintain that retention must be addressed.

"Twitter has enjoyed a nice ride over the last few months, but it will not be able to sustain its meteoric rise without establishing a higher level of user loyalty," Martin says. "Frankly, if Oprah can’t accomplish that, I’m not sure who can."

According to statistics from comScore, Twitter was the fastest growing internet property in March with 9.3 million visitors – a 131 percent increase.