I was going through some support pages at Twitter and came across this:
Your phone is verified and you can send text messages to Twitter
If you were able to verify your phone and send updates via text message to Twitter with no problems, you should be able to receive them. If you can’t receive updates from us, something may be wrong.
A series of suggested troubleshooting steps are given, but then it ends with this strange note:
If you are still unable to receive text updates from Twitter
please let us know. We are still researching this issue and have not found the cause of the problem. In the comments of this thread, please let us know:
With some more steps.
Although I doubt this will impact using Twitter on the Pre, I wanted to make people — Palm and Sprint people — aware of this.