A couple days ago, Google has officially shut off support for version 10 of the AdWords API. A WebmasterWorld thread has one advertiser who is very upset, claiming Google did not warn him.
Our system stopped working today, just as everyone is about to go on vacation for Easter. Just when our programmers are hard to contact. Just when we are most likely to be attacked (our competitors guess we won't be monitoring as closely over Easter).
Seems to only way Google communicated this change from V10 to V11 of the API was a blog post last October.
I feel it is just plain rude of Google to not even bother to email users of the API, to let them know that anything they have developed would stop working today, unless they had rewritten their software.
If the API is that critical to your business, one would think you would subscribe to the AdWords API Blog or join the AdWords API forum to get updates. Honestly, I doubt Google did not email API users about this change before cutting it off. I may be wrong, but I just highly doubt it. I am sure they can see the number of people using version 10 and make that call.
Forum discussion at WebmasterWorld.