Our website already prevented addresses from the same IP, all addresses submitted were from different IPs.
We don't want to let anyone out, so we are working on a solution and we will update soon.
IP is easy to fake. Bitcointalk user name less so. And the initial plan was for 1000 addresses. You will not be letting anyone out but you will be letting many people in more than one time.
Anyway, it's up to you
I don't think it would be fair for all those who participated, specially the last ones.
Our first approach was to do it here in bitcointalk but as the moderators deleted our Genesis Address Collection thread, we didn't have much options in the short run.
Of course IP can be faked (proxies, etc.), but finally all can be faked, even here in bitcointalk one person can hold multiple accounts.
To be fair to everyone, we will make sure that all the valid submitted addresses will be included.
Cheaters can cheat at anywhere and at any stage.
So stick with your rules and go ahead.
Deploy the Smart Contract as early as possible to stop these controversies.
Once this stage is processed, we all can concentrate on Promoting the coin and Listing on exchanges.