bragr parent
That was not a gimmick, that was their core feature at the time. You have to remember that Twitter launched before mobile internet (cell or wifi) was common place, and the fact that you could link your number turned every dumb flip phone into a twitter capable device. Sure by 2010, smartphones had taken over, but for 3-4 years that was one of the main ways people interacted with Twitter.
I meant gimmick in the sense of a unique feature that distinguished it from all the other message boards and social networking things that existed at that time. Nobody I knew used texting to post (because it was expensive in those days of charging per character), but it got a lot of press for being able to post from your phone.