My husband has (had - since we cancelled it) a card with a $500 credit limit from them. When we asked them to raise the limit, they denied it. Meanwhile, we have a ridiculous $30,000 credit limit from AMEX, $15,000 from Master Card and $10,000 from Visa. But by God, $501 is too much for Capital One!
We don't carry a balance on our cards, but use them regularly.