I have absolutely no doubt that this is about monetisation. None. A third party client might be able to block ads, and that would impact Twitter’s ability to monetise. It has very little to do with ‘user experience’, unless the user you are talking about is the advertisers, Twitter’s real customers. If a tech firm is improving the UX for advertisers, it’s almost certainly going to lead to a worse experience for users.
Panzarino was right. Services like Twitter should be considered a public good. The spirit of Twitter belongs to us, the users.
I suppose I have to back App.net now.