WTF holes developed on muffler!

I bought this muffler about two years ago

http://ift.tt/1Eusj1l

Do mufflers need some sort of maintenance? Because this happened...
Anybody know why?

Attached Images

	DSC06949.jpg (97.0 KB)
	DSC06947.jpg (116.8 KB)

WTF holes developed on muffler!