According to a report from Barracuda Networks, a Web security company, most of Twitter’s 50 million accounts merely follow other users rather than posting their own messages. 73% of Twitter accounts have tweeted fewer than 10 times . As of December 2009, only 21% of Twitter account holders were what Barracuda defines as “true users,” meaning someone who has at least 10 followers, follows at least 10 people and has tweeted at least 10 times.More at CNN Money.