Look at what happened to the translate API. How about the licencing changes to Google maps API. They build something like this and if they can't find a way to generate more money (maps API) it gets shut down(translate, now reader.), even if a bunch of people use it. And by a bunch I mean a small collective of tech people.
I would not be surprised to see Google Groups get munched once they finish adding a few more features into the communities bag.
I do use gmail, I have multiple accounts in fact, but I backup everything locally that I think might be valuable to me in the future...just in case.
O.