Well, the OP seems to point at PHP developers generally being poorly educated and clueless, mostly deploying other people's apps rather than writing their own.

Well, the OP seems to point at PHP developers generally being poorly educated and clueless, mostly deploying other people's apps rather than writing their own. In short, they won't have a clue how to use GAE if it provides BigTable rather than MySQL so out-of-the-box LAMP apps fail to work without a rewrite. Does GAE really want user volume if those are the sorts of users they'll get?