First, I've been a member of Pinterest for just a few weeks. I found having to wait to be "invited" rather pretentious though I suppose it keeps out the great unwashed who would infuse the site with unwanted trash.
Here is my experience so far. After accepting the "invitation," I was asked to choose my areas of interest by checking boxes. I came back to the site a couple of days later when I had more time. Everything... and I mean e-v-e-r-y-t-h-i-n-g that was pinned to my account was from the same person who, if the numbers are correct, apparently likes everything that every other member likes only think in numbers that are incomprehensible. I tried to get rid of this person, block her pins, block her name so that I might enjoy a variety of what other members have to offer. Well, apparently the geniuses at Pinterest have no intention of allowing members to block content they find objectionable or redundant. Now... that's scary.
I accessed the "Contact" page and sent a note asking, no really begging, the powers that be at Pinterest to either block from my account what I would consider to be no more than a high-class spammer, and, if they couldn't or wouldn't do that, to close my account. Seeing only pins from one person exclusively at the expense of others whose work and interests I would like to view is not my concept of a well designed social networking/media site. Needless to say, no one has responded. No surprise, really.
There should be a function for members to block other members content they find objectionable or just don't want to see. There should also be a way to close one's membership out.
I think the concept of Pinterest is a fairly good one. There just has to be a lot more functionality for the user to manage his/her account.