Account verification: Only 1 account per person

Question

In my community, every user should only have one account.

So I need a solution to verify that the specific account is the only one the user owns

Answer 1

Have them enter their phone number and send a text message to it. Then, keep a unique of all the cell phone numbers. Most people have one cell phone, and aren't going to ask their friend to borrow it just to create a second account.

http://en.wikipedia.org/wiki/List_of_SMS_gateways