APIs shouldn't change in backward-incompatible ways. That's sorta the bedrock of a service oriented architecture. If teams have to communicate with each other through more than API documentation and can push responsibilities onto each other by making backwards-incompatible changes then you've kneecapped the entire benefit of a service oriented architecture from the get-go.
I'm not talking about backwards compatibility so much as adding features in parallel that span many services, which happens when you're closing a lot of sales deals when the salespeople don't say no to things :p