Who hasn't heard of desu? It's a spam word seen commonly in /b/, on 4chan. It is rarely used in actual Japan, and orignated from a Rozen Maiden character who finished her sentences with it.
Read up on desu here: [link]http://www.encyclopediadramatica.com/index.php/Desu[/link]
The reason I don't recommend reading up on it in wikipedia is well... find out for yourself:
http://en.wikipedia.org/wiki/DesuStephen Colbert put desu on notice! If he put it on notice, you know it's a problem!
So many people have forgotten that "desu" only sounds cute when an anime girl says it. When a real life dude says it, he looks like a noobologist.
Discuss upon this subject!