The Stackoverflow FAQ for voting a
closed question states
Users with 3000 reputation can cast up to 50 close votes per day. When a question reaches 5 close votes, it is marked as closed, and will no longer accept answers.
Another question on Meta Stackoverflow adds that
Moderators may close any question (regardless of their reputation). This implies that a question on Stackoverflow may not receive more than 5 votes to be marked as
closed. However, I see a few posts which have more than 5
close votes. Here is a list of some questions (there are 17 such questions according to the August 2012 snapshot) which have more than 5
close votes on it-
Is this an anomaly or am I missing something?