I know of at least one serious incident last year with this happening. And at least two not so serious incidents this year of it hapenning.
Out of, what, 30,000 tournament entries?
One drawback is that it isn't needed at lower-tier tournaments, while at bigger tournaments, it would more greatly add to the hassle. Imagine checking 700 IDs at Bowling Green. Or 1000 at Charlotte Worlds. At 20 seconds apiece, that's 6 1/2 hours just devoted to checking IDs.