Very nice site. I've been checking if it is working almost every day
I think that when you have time you should think about the following:
I think you should secure the pages(so that you will be confident that a human is reading it, not a robot), which contain profile information about the user such as email address.(The machines can get smarter and recognize the type of scambeling you have now). One way to do this, is to ask a question, which only a human can answer. Like show some digits as an img, and ask the "user" to write these digits. If the digits mach, then you let them thougth, else you show fake information.
You can see what i am taling about on this page, althought it is in russian,you should see an image with numbers, and provided blank space.
http://www.beeonline.ru/portal/comm/sen ... nd_sms.sms
Anton