By cutting off developers, Twitter has effectively cut off their own future relevance. The web is moving aside in favor of mobile apps, and Twitter must eventually adapt to this world or watch as another service eats their lunch.
Why I’m Supporting Twitter Competitor App.Net, Even Though It Will Fail
Twitter is unstoppable, so why did I just pledge actual money to support App.Net, a competing project that will most certainly fail? Because twitter is too important a communication channel to leave to Twitter, Inc. And they need to hear from us, the users, before they destroy their service.