A few months back at a tournament, I saw a teenager (6ft and built like a linebacker) pick up and drop a MB after he drained with a great big slam. He acted like a fairly angry person even before the tournament started. I don't know what the aftermath of that was, but the room kind of went a bit quiet when that happen--no easy feat in a noisy room filled with pins.
At the show I was at this weekend, I was told that someone got angry they drained on my RFM and shoved it back a couple of feet. And that is a pretty heavy game. Supposedly, the guy was chewed out for doing it. I didn't notice any damage, thankfully.
By the end of the show, the playfield glass on my RFM ended up with several new scratches, so I imagine people were putting stuff on it for some reason. I'm not particularly happy about that. Pins aren't tables, and I see people putting bags, purses, drinks, and whatnot on games all the time. Whenever I see that happen I ask people not to do that.
I sure as heck don't want scratches in a brand new sheet of glass, or an expensive sheet of glass like the one found on pin 2000 games. I'm almost tempted to try covering the glass in mylar, though I'm not sure if that would prevent the reflective properties of the glass from working properly.