I tried pinterest a while back (so apologies if it's changed since)... I remember the sign-up process was awful. Part of the sign up process forces you to follow a certain number of other people. I just wanted a blank page to start adding to. If I'm signing up to something "social" with my name attached, I don't want to be forced to publicly follow other people/groups that I haven't fully checked out.

The sign-up process was so in-your-face and demanding I gave up and never came back.

(I'm male, if that makes any difference or relevance).