My understanding is that when large denomination chips (like $1000 or $5000 chips) are issued, one can link the ID for each chip to the person (say, through their players card) who was issued the chips. Say, for example, someone takes out a marker for a large amount. If someone else were to cash in one of those chips, then the casino may suspect the person was giving out interest free loans to friends or some other monkey business.

I must confess that I haven't played very much at the Wynn in the last year or two, so I don't have any real world experience with what they're doing.

Re: the Hard Rock - I play quite a bit there, and am almost certain they aren't using RFID on the main floor for their chips. Of course, the highest denomination chip I play with is a black chip, so I may be missing something. Their high roller pit, the Peacock Lounge, may make use of the RFID chips. The thing about the Hard Rock is that they issue new chips fairly often, and they tend to become collector's items. I don't know how often they issue collectible chips above $25, but I would think that they wouldn't want to invest too much in the technology if the chips are just going to sit behind a display case.