Yes, if you click on the pins they do lead back to your gallery...so proper credit is therefore given even if the pinner doesn't give it in the decription on their pin.
I can understand why someone wouldn't want there stuff pinned w/out permission. It's almost like a "loss of control" over your layouts, and this can feel a little like a "loss of control", albeit a small loss, of your life. However, I am not uncomfortable w/ it so as far as I'm concerned...if you like my work... pin away!
I just wish I could see exactly who was pinning my layouts...it's just a curiousity thing.