It happens in more places than just Denny's. Just imagine how many go unreported.
Probably less than you think, since the Denny's lawsuits clued people in that getting-refused-service = big-bucks.
...
Every soft pad I've ever had has done that (i've had about four). Sometimes it helps to make sure they are really flat on the floor, cause if they get folded a bit it can cause scrolling.
but if you ...