Not sure why you think Twitter's application was rejected. That's the problem with relying on sensationalist blog posts that have no idea what they are talking about. I posted extensively on DNForum about Twitter's application & response. USPTO has not rejected the application, it simply awaits a reclassification, as 2 more "tweet" marks from Retweet and Tweetpics are in the same class. There is no outright rejection of the application.