We've written about Paul Adams a few times now. As a refresher, he's the guy who used to work at Google on user experience and made a popular presentation that suggested how Google could go after Facebook in the social space — namely, friend groups. That, of course, ended up happening with Google+. But before that project was complete, Adams jumped ship to, where else, Facebook . After the recent launch of G+, he stated that seeing it was a bit like " bumping into an ex-girlfriend ". Yes, that guy. Anyway, there's been a lot of interest recently in Adams given his history and he took some time today to write a blog post to clear some things up. Why he left Google, what he does at Facebook — it's good stuff. But the real meat is one little nugget of information he drops: Google is blocking him from releasing a book he wrote about his social research called, what else, Social Circles . And Adams is not happy about this at all.