I have an account on StackOverflow, ServerFault, and SuperUser all linked to the same OpenID. I originally did not think much of it until I noticed I started gaining reputation/badges individually on each site. Are you supposed to gain reputation per each site, or if the accounts are linked is it supposed to be summed across all of StackExchange? I can see all of my accounts in the 'Accounts' tab of my profile, so I am guessing they are linked together (but not merged? if that means anything).