I have mixed feelings on this myself. I've gotten away with a stealth sbd, was a digitial patch. no issues at all. Band normally allowed, but were recording the performance themselves. (and for those who ask, I havent traded the tape.. or listened to it in over a year! so not getting out there from me!). So, ONE time experience for me, and thats it. I dont think you could fuck up a spdif patch!
I dont even see where you'd be able to get near a board and plugin w/o getting caught by the soundman. Of all the venues I've been to, I dont see how youd get back there w/o being noticed...
IMO: buddy up to the local soundguys, and more often than not they'll hook you up with a patch even if the band doesn't allow board patches... drop them off some cdrs of other shows you've taped. They like that gesture. And its a lot better to have them plug your ass in than doing it yourself!!! Maybe if they show you, where, etc.. but to do it on your own... I'd be very hesitant.
Now as far as relating a stealth board as stealing? I dont know about that. your still just taping the performance. Same lines as an IEM/ALD. Still just taping (altough the quality might be a lot better). I guess I'd call it stealing if you were selling it on ebay or something, but for a private collector to listen to.... kinda hard to figure out where that fine line is..
-T me away I guess!
-Jim