I asked to join and got the same email. Then the next day I got one saying I was in. But when I found out I had to use Facebook, Twitter, or something else I don't do, I declined. I use something called visualize.us that is also a way to save pictures or projects I want to go back to, but it doesn't cost anything and you don't have to be invited. It's not as flashy as Pinterest, but it works for me. If I want to go look at someone else's pins, there are several bloggers whose taste I like, so I can just go look at their pictures.