Ugh, yes. The MagSafe silicone case I bought last fall got nicks in the corners within a few months of use, and they've been slowly but steadily growing ever since. Supposedly the case has a one-year warranty and I can take it in to get swapped out, but I haven't tried yet.
I'm worried by reports from people saying they took theirs in to Apple Stores and were denied replacements. I wish you success and hope you don't end up one of them.
