The graph below speaks for itself, but I’ll tell you anyway: Twitter is at the 6 million unique visitors mark for January. Good news for Twitter researchers like myself. A recent study by Pew Internet also notes Twitter’s surging growth:

As of December 2008, 11% of online American adults said they have used a service like Twitter or another service that allowed them to share updates about themselves or to see the updates of others.

Twitter, rock on.