I was a happy Google Talk user who had written a useful App Engine chatbot. It was really easy because App Engine had built-in XMPP support and each one had its own built-in address, so handling chat messages was even simpler than handling HTTP requests.

But then Google stopped supporting XMPP from other domains (including their own domains) in their chat apps, which meant that I could only use my Google App Engine chat bot from non-Google chat programs, and that was a ridiculous situation.