Even worse is the "Why not try X, your friend Y is."

This was especially fun in my case when, under the heading "You might like" I had: "<girlfriends name> just signed up on <dating site>". :)

I don't entirely mind them profiling me based on what I choose to put on Facebook. But leaking it to my friends is weird.

(I know you can restrict the audience for everything you do, and I actively do this, but it is soooo easy to slip up).