It's true. I knew a guy that was and over brusher and was having problems with his gums. He thought it was an issue of him not brushing enough, so he brushed more, and harder, to make sure everything was spotless. When he went to a dentist, they told him he was brushing too much and should back off.
Sorry, but yes, you can also floss too much. Once a day is all you really need unless you're getting something out that is stuck between your teeth.
Disclaimer: I'm not a dentist.