....
Man its not impossible to trick any system.may be he created accounts from separate ip/device or asked his friend to create an account for him.But a underdeveloped country like us (BD) its hard to trick an online system where a few cities have the dedicated ip,while other thousands of people are using same ip provided by the ISP. I can verify my identity for bounty if iconomi need that to do so.
Call twitter/facebook spammers by skype this is solution on twiter facebook you are public anyway .
No skype verification call - forget your bounty.
Bots and spammers will give up fast : )