FYI, there's a difference between a tradename and a trademark. Depending on whose jurisdiction we're talking here, the two might not be the same. In the U.S., a tradename is simply the name of an entity operating a business. A trademark is a word, phrase, logo, symbol, or a combo of any of them used to identify the source of a good or service in commerce, and a tradename will not grant its registrant trademark rights unless defined by any applicable law. For example, I have a business whose tradename is Dave Zan Enterprises that sells Torch bowling balls. Dave Zan Enterprises is my tradename, while torch is my trademark for bowling balls. But if my business whose tradename Dave Zan Enterprises also sells Dave Zan bowling balls, then my tradename is also a trademark. Make sense? Feel free to search around to verify what I posted. And let's put it this way, folks. Currently Twitter doesn't seem to make this an issue, but...they very well can in the future and subsequently create problems for those whose domains bear their trademark. As I'd usually tell myself: hope for the best, expect the worst, be prepared.
Don't ever try it with the brand Rolex. I didn't even get the site up before I heard from their legal department. And, they never paid me for the domain name either. Art