Battery cover scrached

I was cleaning up the finger prints and such off my computer this morning and realized that on the bottom, only the battery cover is really scrached up (much more then I would expect for a only having it a few month) anyone elses like this?

What kind of surface do you use the Macbook on?

My desk, There isn't anything I can think of that would have done that amount of scraching. It's only on the battery cover and no where else.