It's clear that Twitter wants to move innovation in their ecosystem away from native clients that duplicate their exiting functionality. Instead they seem to be keen to support projects that offer innovative ways of displaying, sorting, or working with Twitter's firehose.
Instagram does something similar. Their API terms of use read:
"You cannot replicate the core user experience of Instagram.com"
(http://instagram.com/developer/)
I guess it is a matter of keeping potential future monetization options.
So pretty much a shit sandwich from Twitter. The thing is Twitter probably would not have been nearly as successful without all the 3rd party mobile apps, and now Twitter is screwing with the people that contributed to Twitter's own success.
I wouldn't even call it that. They bought out Tweetie and made that their official client, then proceed to make it a pain in the ass for all other Twitter apps.
Instagram does something similar. Their API terms of use read: "You cannot replicate the core user experience of Instagram.com" (http://instagram.com/developer/)
I guess it is a matter of keeping potential future monetization options.