Not to woz up this thread, but a couple of years ago I went to the bank to withdraw $1500 in hundred dollar bills for a trip to Vegas. I ended up not losing any money so at the end of the trip, I was going to pay my remaining balance at the Wynn with some of the hundreds I brought with me (they'd been in the safe the whole time since I never needed them). I took them to pay which I thought would be quick... they took the cash to the back and a called a bunch of people over. After about 10 minutes the hotel services person came over and said the bills were coming back counterfeit and asked if I could pay another way. I paid with a credit card and they gave me the "counterfeit" bills back.
When I got back to Dallas, I took them back to the bank I withdrew them from and told them the story. They checked them and said, "These aren't counterfeit" and deposited them back in my account.
I've always wondered why they came up counterfeit at the Wynn though. Maybe their machine is ultra sensitive or something....