The debate over whether or not Twitter is a useful marketing tool is still raging, but there's a new debate brewing about exactly how many consumers are still using Twitter.
One thing is for sure: Traffic to Twitter.com is declining month over month. New data from Nielsen shows Twitter traffic dropped 27.8 percent between September and October, bringing it down to 18.9 million unique visitors, according to eMarketer. Meanwhile, comScore reports that uniques are falling by 8.1 percent, with Compete reporting a 2.1 percent drop.
The decline in visitors to Twitter.com could indicate a migration to third-party applications like TweetDeck or Tweetie. After all, Twitter 's popularity is partly fueled by the ability to share shorter, SMS-length messages on a mobile phone. No one has offered a definitive figure for the number of users who access the service through third-party apps, but one estimate, from Crowd Science, pegged it at 43 percent.
Twitter experienced meteoric growth throughout 2009, and 18 million U.S. adults will use the service by the end of the year, according to eMarketer.