MacBook Pro 15" reoccurring oily patches on screen

Question

I have an early-2011 version MacBook Pro, new out of the box this mid-October. Within the last month I've noticed reoccurring small, oily patches appearing on the lower third of the left-hand side of the screen, especially after the cover has been closed for a significant period of time (like overnight).
The patches show up in about four places, in varying sizes, and always in the same place on the screen. The substance feels oily and is iridescent against the lit screen, but when wiped away with a clean soft cloth, disappears without smearing. When the patches reappear it's a relatively slow process — after I wipe the screen down I usually don't notice the spots again for several hours, and, I think, only if I've closed the cover. I haven't yet tested to see whether this happens only when I've closed the lid without sleeping or shutting down the Mac, or happens no matter the circumstance. 
I don't believe the substance is coming from the keyboard. I use a Moshi Clearguard keyboard cover and I've checked the corresponding areas on and under the cover and on the keyboard, and there's no evidence of oiliness. By the same token, there's no visible evidence of damage to or imperfection in the screen.
Right now this is merely annoying and unexpected, but I don't want it to create a major issue should it worsen. Has anyone else experienced this?

Answer 1

I'd bring it in, thats what your warranty is for.