Ask HN: Is it possible that FB and Google are sharing user data?

Paging through my friend suggestions on Facebook today I saw many familiar faces. I corresponded with all of them on GMail but we never had contact on Facebook. We have no mutual friends, I've never looked at their profiles, I'm pretty sure some of them don't even know my real name so they couldn't have looked at mine. I never gave FB access to my GMail account so I'm struggling to understand how this could be. I realize that network analysis can sometimes be effective but this looks a little too good to be true.

Any ideas?