Spammers can provision an unlimited number of email addresses, so you won't stop a spammer by requiring him to validate an e-mail address. I can think of three

Spammers can provision an unlimited number of email addresses, so you won't stop a spammer by requiring him to validate an e-mail address. I can think of three reasons you want to validate an e-mail address like this: - Confirming that you've typed your e-mail address correctly and that it is reachable - Preventing you from impersonating someone else - Opt-in for sending you e-mails. Not really to prevent you from spamming/harassing/annoying someone else (there are many ways other ways to do this), but to prevent the service from having e-mails marked as spam. I'm sure the last one is the strongest, as being blacklisted from one of the big e-mail providers would really hurt most online services.