I think the key thing here is 'what are we betting on?'. The analogy to Facebook doesn't work, as the developers have bet on different things. The apps that Twitter are calling out are ones that are trying to replace Twitter itself as a consumption device for end-users. Can you name one major Facebook app that does that? I can't. When Facebook saw a good pure social innovation in an app, they didn't hesitate to copy it. However apps that have built on top of Facebook to add value in different ways have been actively supported by Facebook for years. Twitter themselves in the announcement make this distinction - do something different than just trying to replace us for end users (e.g. a business management tool, a cool data analysis tool) and we'll support you; otherwise get lost.

I don't really think this is hostility - I think it makes sense for Twitter and for developers; people who've just been trying to replace Twitter themselves were always fighting a losing battle.