I just got back from a trip to England, and while in London, I was sitting down taking a break from a long day, and forgot I took the camera (20D) off my neck and had it sitting on my lap. As I stood up, the camera tumbled off my lap and fell onto concrete. Yikes.
Well, to make a long story short, the camera and lens are pretty tough. The camera is fine, and the lens is mostly fine. The 24-105 hit right on the front where the lens hood attaches and right away you could see it was scraped where it hit, no big deal, but when I got home two nights ago, you could see a faint hairline crack that is probably less than 1/8" long right at the very end. Its not even enough that you can see it unless you hold it in bright light. It doesn't affect anything, even the attachment of the lens hood.
Now, let me stress it's no big deal, but I was curious if that piece could be replaced by itself, and if so, does canon sell parts like that?