I had to wait a while (because only one attendant) at a small airport Avis desk (where Preferred have their packet and key ready but it's behind the desk, since the cars themselves are in an unattended area) yesterday, and the reason was because a new staff member earier in the day had given the reservation of the person in front me (at 5 pm) to someone else (at 12:30 pm that day). Apparently they both had the same (very common) first name and same ("Brown") last name, and the new hire didn't check other stuff.

I have a fairly unique name, so I'm not expecting to ever have this problem myself. But I wonder if it'd be less likely with a Wizard number in there? (The person in front of he had booked through Southwest, no Wizard, and I suspect the person at 12:30 also wasn't Preferred.) I presume if you are Preferred (or above), and the other person with the same name as you isn't, then they won't as likely confuse that.