Were developers notified at all this was going to happen?
Purely speculating--but I bet they discovered that their APIs were open for privacy abuse, and rather than just disable the abusing accounts, they shut down the APIs until they can be fixed.
I also believe this is a reaction to all the recent privacy issues that Facebook is facing. They identified Instagram as a huge risk for behavioral mining (it is) and abruptly shut down all features that can be used to analyze behavior and infringe on privacy at a large scale.
The application felt like I was begging. Not something I'd ever do again.