Prevent users from starting multiple accounts?

Question

I know that in the end it, can\'t be done.

But, what are the options to:

  a) limit the options for persons to create multiple accounts,
  b)

Answer 1

I think, as many people have mentioned above, one of the best ways is to verify mobile numbers and that's what I wanted to use in teh first place, if it wasnt so damn expensive ...

I have found this site here and I think it can be used for this purpose but I havent tested it myself, but it seems pretty modern and cheap