I just got this in an update from the TxtMob guys:
Finally, a note for T-Mobile customers: As many of you are aware, T-Mobile blocked TXTmob messages during a portion of the RNC. While we won't speculate on the reasons for this action, it would be extremely helpful if the hundreds of customers who were unable to receive TXTMob messages called T-Mobile to complain. Be sure to explain that TXTMob is an opt-in service that you have chosen to join, and to encourage their representatives to contact email@example.com if they have any questions.
I think that T-Mobile should explain themselves. Was it a glitch (probably not) or did some pro-Republican paper-pusher purposefully block TxtMob messages? Who's service is next? What if they don't like your text messages - are they going to stop sending those as well?
If it was a problem, fine. If they're playing Big-Brother they need to be held accountable.