I came across this question - Sql Server Will Index Help Here on SO and if you read the comments on the question, the OP claims that he is not registered and hence cannot up-vote.
The profile of OP shows that he is a member for 56 days. http://stackoverflow.com/users/572140/joda-maki
I am confused if this is expected behavior from the system? Why is OP not able to up-vote for any of the answers whereas he has been able to accept around 30 answers for his questions?