Not unexpectedly, Twitter has recently expressed discomfort with the legions of Twitter-propagating services that incorporate the "tweet" or similar formative into their names. My take? Without such services as TweetDeck or Tweetie, Twitter would not be the phenomenon it is today. So I think what we have here is a new category of generic term: a noun or verb form of Twitter, which is clearly an arbitrary and registrable mark, meaning either a message sent on Twitter or to send a message via Twitter.
Try this for an analogous situation: ROLLERBLADE creates an entirely new form of skating, and has to scramble for a generic term, in-line skating, in order to preserve its trademark rights. But that hasn't stopped the world from using "blades" and "blading" or registering "blading" in connection with skating, with the result being that Rollerblade has great public mindshare.
The way I see it, if all these tweeters are driving traffic and mindshare and users to Twitter, who benefits? Twitter. If Twitter starts going after all the Twitter-propagators, who looks like a trademark bully? Twitter. And if the Twitter-propagators have to change their names to something less suggestive of the Twitter service, who loses? I'm just saying.
H/t to Nancy.
(And yes, I think I'll tweet this via Twhirl