I have the same problem as Joann, with my cotton t-shirts getting holes around the belly button area. It must be mechanical, because it's only in one spot, and I figure the fabric must be different, since it seems to be a new problem. I'm wondering if this is more likely to happen to those of us whose belly might be just a little on the protuberant side, :o as this would cause more rubbing on counters, etc. It never happened when I was skinny, although if it's because of a change in fabric this wouldn't matter.
So, I'm posting an anonymous poll for those of us that wear cotton t-shirts. :) Give me a minute.