A lot of times people will black out and not realize they've done stupid drunk ass like shit. And mixing it with alcohol/other drugs is of course dangerous. I know people who have blacked out and accidentally shot like a gram of heroin when they normally can only handle .2. I've blacked out and had an suv on two wheels for a good 10 seconds, everyone in the car tried to move to the otherside to make it fall, numerous other stories. But most don't remember.
That's one of the main things people wonder about getting fucked on benzo's. Some would argue if you're too fucked to remember how is it fun? Others live in the moment and go nuts. Just a lot of the time when you're that fucked you won't remember shit, or atleast bits and pieces, which are often filled in by other people. And if you're filling in someones memory you can tell them a fake story and they'll believe it. One of my ex girlfriends was told she had sex with me, before we ever hooked up, and she believed it, called me the next day at 3am apologizing