More often than you might imagine...
That's the dark secret of the laser industry. There aren't a lot of enforcement people, so it's fairly easy to fly under the radar. Unfortunately, the guys that do this are the reason it's so damn hard for the rest of the legit businesses out there. (If they're willing to take a short cut on the paperwork, they're willing to take other, more serious shortcuts. That leads to accidents, lousy shows, technical problems, etc, which reflects baddly on the industry as a whole.)
I've been to a club where they had static beams firing directly into the crowd from a mobolaser beam table. Now, granted, most people will probably blink before they get hurt, even when we're talking about a couple hundred mw of power. But nonetheless, that sort of thing is clearly against the rules, not to mention reckless as hell. I saw one of the lighting guys in the john later that night and asked him if he had an IR filter on his green DPSS laser. He just looked at me and blinked, then shrugged his shoulders and walked away. I haven't been back to that club since...
The down side is that in the unlikely event that you do get caught, you aren't dealing with the town police or the local sherriff. We're talking the United States Food and Drug Administration baby... And when provoked, the government takes strides in 7 league boots...
Personally, I'm going to get a variance. Even though I might not actually ever do a commerical show, I might do some more demos at schools and stuff. I figure a variance will help in two ways - 1) I get credibility as a safety-conscious laserist, and 2) it deflects potential liability because I'm already approved to FEDERAL standards.
BTW, for the record you can apply for a projector variance and a traveling show variance all at the same time. The last guy I talked to said it took about 4 months for his paperwork to get processed. (He got both variances.)
Adam