I went to replace my cables and housing this weekend, when I noticed my rear derailleur cable was rubbing on my frame. The cable exits the guide and cuts across the frame before going to the RD.
I never noticed it before, but it I guess it's been doing that since I bought it in late 2012. The cable has worn a nice groove into the frame. I've talked with my LBS and sent this photo, among others, for a possible warranty claim. The LBS said they've not seen this happen on any other bikes.