http://blog.twitter.com/2009/07/may-tweets-be-with-you.html
Twitters stance on this is the correct one for their brand in some ways and so it’s important to understand that you as a company should have never gone into those waters in the 1st place. Your brand is your world and building someone else ( especially when platforms continue to change every 3-4-5 years) is much more of a bad play then just getting slapped with Trademark issues!

I talked about this a few months ago at the 23 minute mark of this keynote

Big Omaha - Minute 23:00

“I really hope that people understand, like here’s what drive me crazy, when I see products like Tweetie or Twitterrific I’m always like, ‘nooo don’t you know what’s going to happen?’ You know facebook’s going to open up and then you’re going to want to have the open, you know, API to facebook status but now your called Twitterrific so it’s a little niche and then…You know, just keep that in mind if you’re a serial entrepreneur and you like to do niche little businesses, keep in mind that whatever the hot thing is at the time, it’s going to be the hot thing of the time so go with maybe a little bit of a more global name that you can like bring that into. There’s just going to be new things, its always going to change.”