If it seems like Twitter is growing faster and faster each day, that is because it is. ComScore has released its March numbers for the U.S., and it estimates that unique visitors to Twitter.com grew 131 percent between February and March to 9.3 million visitors. Not only did Twitter more than double the number of people that go to its site in a single month, but it accelerated its growth from the 55 percent rate it experienced in February.