I'm not being paranoid. I'm being realistic and even taking notes.
I've got a gmail account, as well as most other things beginning in "g" that Google's come up with. But I've only recently started to notice how really well they know me.
Opening a mail about a concert - the right margin will fill up with advertisements on how to buy tickets for concerts, how to find concerts etc. I wrote about the coeliac disease in a mail - the margin showed me gluten-free recipes. I wrote about a card - the margin showed me where I could find e-cards. And so on and so forth...
I'm presuming it's a machine doing these things, not an actual person. (What a boring day they'd have, reading through my mails...) But still - what's a machine doing reading my mail? Is there no such thing as privacy? Or are we all such good friends (after all, you need an invitation to have a gmail address, don't you?) so we ought to share our mail content with the world?