They're definitely on every Atlantic city and las Vegas table I've ever seen. But they blend in and are very subtle. It's just enough to make the dice tumble if they're being slid instead of rolled. Most people never even think of it because the stickman should be telling you to throw the dice to the back wall anyway. Next time you're at a table look in the middle right in front of the boxman.
In andy800's example you can see it under the felt but I think I have seen them over the felt as well, but either wat it is very subtle and you won't notice it if you're not looking for it. I had played craps for over a decade before I read a book that mentioned it, and since then I have noticed it every time.
There is a very subtle North-South bump under the felt, directly in the center, under the words "CRAPS" and "DEALER and PLAYERS" and "Seven". It might be easiest to see at the lowest horizontal line, below the words "Any Craps."
