In 2013, Twitter introduced a new policy that was designed to prevent third-party Twitter clients from gaining too much popularity. The design to the Twitter API basically capped the number of API “tokens” a third-party developer have. Each token is tied to a user, so the effect is that if a third-party Twitter client gets too popular, Twitter will stop allowing new users of that app into the service.
Over the weekend, it appears that Tapbot’s third-party Twitter app, Tweetbot for Mac, finally ran up against its token limit… and as of right now, has been pulled from the Mac App Store.

