I've read in a few places some statistics to indicate that people with zero CC balance have a lower average credit score than someone who maintains a low, yet nonzero, balance. What is the mechanism of this, if it is actually a real effect? Another possibility could be that those with zero balances don't use credit and don't have a significant credit history, leading to a lower score.
I can't swear that it's real but one of those pseudo-credit scores you find online considered it a ding on my credit that my utilization was 0%. They were being stupid about it, though--it's not actually 0%, just less than 1%.