I searched and found that "cannot" has been used in 72 different Community Board posts in the past two weeks alone (though that includes some posts where it was just quoted from someone else who actually used it). People who have used it include nossy, Legolas, Joel, Stephen, DomA, Camilla, Cannoli, Bergioyn, and me.

And because you cannot remember the last time you saw someone use cannot, I have taken the liberty of finding it for you!

http://www.readandfindout.com/community/messageboard/260343/

It was nine days ago.