UUIDs have always seemed to be an over-engineered solution to a minor problem. In the cases I've seen them used folks are trying to get away from auto-incremented identifying serial numbers. Ostensibly, this is because it makes guessing other IDs in the database (or whatever) fairly simple and that could be a source for leaking information.

To me this is just security though obscurity. Just because I know an identifier doesn't mean I should be able to do _anything_ with it. If there are contexts where you really can't share the ID you should salt and hash it and use that value.