It's sad to say, but intrusions happen more often than you think. Some guests just aren't smart enough to realize that getting out of their ride vehicle is a bad idea. Of my former dark rides, Pooh and Snow White, only Pooh had intrusions. They are in areas where a guest could get hurt if they were to get out of the ride (Owl's house and where Tiger comes out of the tree) and also at the end of the ride. Guests apparently enjoy getting out of their vehicles to take pictures during cascade stops at the end of the ride. We tended to only have problems if a group of teenagers (usually males) were on the ride and thought it was funny to get, out or if someone accidentally dropped something and triggered a sensor. By the time, the CMs do a walk through, the guest who got out have already gotten back in. There is a computer system that tells you what sensor has been triggered, but we all know Disney can't accuse anyone of anything.
As for Snow White, there is no intrusion system. So any guest can get out any time they want. It has happened multiple times during grad nights. This is the reason why Dopey and Sneezy no longer have instruments in the cottage scene. This also is the reason why Dopey's hand is broken is the scene with the witch on the cliff. You can't tell his hand is broken unless you really look. But it's horrible to see what inconsiderate guests can do.
Of course both of these rides have lap bars, and they obviously do nothing. Positively the doors that have been added to Pooh has cut down on the number of guests jumping out at the end of the ride. It's just too bad that certain guests have to ruin the ride for everyone else.