Since I only use one card and pay it off in full each month, I forget that my Citibank has been unused for months. After a little googling around I learned that HSBC, Chase, and Bank of America have been known to close accounts due to inactivity. Sometimes an inactive card might be your oldest, and therefore a jackpot number in your credit score. Credit card companies closing accounts willy nilly can have some serious consequences.
So last month I did some research at Charity Navigator, along with a few charities I already support, and put my previously inactive credit cards on automatic monthly contributions. I'm not sure if charging ten bucks a month will prevent them from closing the accounts, but it's not exactly like they're handing out credit cards like they used to, and I've grown fond of my credit score.