What about hand stamping?
For example: You have the organizers of the event, you have a number of dealers, you have the participants, and then you have the those that don't fit into those categories. They may be parents or friends, people that just want to hang out. There also may be those that come with no intention of doing anything other than trading, watching, whatever.
Bear with me for second. . .
I have no idea what category a thief may fit into. Its probably more an opportunistic action than not. So would cutting down on the tight intermingling before, during and after matches help? Participants get their hands stamped and stay in the main seating/playing area - this is a lot of people to deal with anyway. So, those without can hangout over by the dealers' tables where there would be those extra tables I always seem to see at the events and/or the feature match table.
It may cut down on traffic. It may make the judges better able to get in and out of the rows easier. I don't know. I'm just throwing things out I think seem reasonable. To me, this seems to add minimal extra effort for the benefit of discouraging theft. Other than a few dollars for a stamp and ink and an extra body to do it (yes, I would volunteer to help with this) it seems to take little extra effort.
As usual, my disclaimer: I'm not a TO, I've been to a decent amount of events but only as a player so please discuss. Oh, and I promise I will never get to the point of metal detectors and bag and pocket searches. Let's leave that in the high schools where it belongs.Â

Richard Raupach, LPCS
Sr. Claim ExaminerÂ
Father of four future magic players