Exactly. Google accounts have so many uses (gmail, youtube, google code, google docs, picasa...), it would be easy to detect how "active" / "real" an account is

Exactly. Google accounts have so many uses (gmail, youtube, google code, google docs, picasa...), it would be easy to detect how "active" / "real" an account is. Of course, anything can be gamed... But it's better than nothing. If I were to create a web-app with user-generated content, I would try to create a "trust" system based on a "reputation" / "real person" metric. It may come from his StackOverflow / reddit / HN reputation, his Google Account activity, Facebook activity... Before buying a product based on a review I read on a forum, I always look at the author's post count / history / reputation. That's why I like HN / Reddit and their Karma systems. We need to automate that