17 August 2012Twitter Developers Blog:
If your application already has more than 100,000 individual user tokens, you’ll be able to maintain and add new users to your application until you reach 200% of your current user token count (as of today) — as long as you comply with our Rules of the Road. Once you reach 200% of your current user token count, you’ll be able to maintain your application to serve your users, but you will not be able to add additional users without our permission.
Effectively, all third-party clients now have a limited growth potential, and therefore, a limited shelf life. No one will want to develop a client anymore.