At the time, you could only use twitter via sms. It's since become much less tied to SMS. I'm not even sure if you CAN do the whole signup and user creation via txt message alone anymore.

The problem with txtmob was the group creation process was always clunky. If you could solve that, make it easy to create groups and start participating, then it might still take off. At one point we even had a version of txtmob which let you sign up and sign off via asterisk, using voip. Looks like pretty much what you did. That was after twitter launched, so we never really put a lot of work in to making it stable.

I still think it's a good idea, i say go for it! Hosted VOIP as a service makes it MUCH easier to do this today, than in 2004-2006.

[edit] - after reading that I do remember hearing about this while reading about the beginnings of Twitter. Unfortunately when brainstorming domains I did not recall TXTMob.

To clarify, I am not going to use the phone numbers in any way. I do send them over to Groupme (to add to the group) so I cannot speak for them. This is more of a pet project currently and am not going to be spamming the phones or anything. I just wanted to see if people like it.

I agree. I should throw up a privacy policy. Any easy policies to throw up?

[Edit] - I posted an explanation as a placeholder Privacy Policy. No legal language, but it at least clarifies things.