You cannot add new accounts though due to [Twitter’s new API restrictions](http://www.marco.org/2012/08/16/twitter-api-changes)[^fn1].
[^fn1]: As [The Beard](http://www.loopinsight.com/2012/08/31/tweetbot-for-mac-beta/) says “Amazing that these developers are still trying to improve their apps and Twitter can’t release an update for their piece of s\#$t app.”