Last year I wrote about the brilliance of platform APIs for the big guys:  let your app developers figure out what the market wants, and then incorporate those into your system.  Most API terms prohibit you from suing the platform provider, effectively giving them a non-exclusive license to everything you do.

Now, we have examples of Facebook absconding app features.  From VentureBeat:

Facebook has a history of mimicking the functionality of hot services around the web. Your status updates weren’t always there, you used to have to go to Twitter to do that. Then Facebook rolled out that functionality in a way that looked eerily similar to Twitter in some regards.