Well, there are three ways to look at this kind of thing:
1. If you're talking about an actual "band" made up of regular people who hit it big, then sure - mistakes can happen. It's usually no big deal unless it becomes a problem. But if you're in Rush or one of these other legacy bands, where you built it and you own it, and you're the boss anyway, you could mess up all night. Heck, go out and set your bass on fire. Wouldn't matter. But, an interesting thing about this was the Bon Jovi episode of Behind the Music, where Richie Sambora is talking about Alec Jon Such's terrible live playing. He said, and I'm paraphrasing here, "At first, I felt bad for the guy, making mistakes in front of these huge audiences. But after it kept happening again and again I started to feel bad for us, and for the audiences getting that kind of performance." Good stuff right there, Sambora. Anyway, Hugh McDonald played all the parts on their records anyway, so it made sense he'd take over live after Such was fired. Thing is, though - you go out and play a set in a band where there's no (or very little) improvisation, things are inevitably going to get super tight. If they don't, someone's a problem and they've gotta go. There were always these killer drummer gigs coming up for grabs around LA when I was in that circuit, because when bands were getting signed in the early 2000s (not sure how it is now), like 9/10 times the drummer would be canned and replaced by a pro who could keep time and make it slam on tour. That happened constantly. Anyway, speaking of hired guns...
2. No, they don't usually make mistakes. If they do, you'd never know it because they'd cover up. But if they kept on making mistakes they ain't gonna have the gig for long, at least if it's high profile or one where the MD takes his gig seriously. Go to a Rickey Minor clinic and he's got no problem telling you he fires players constantly. One strike, warning. One more? Gone. A lot of these gigs go to players who are insane with both precision an feel, in that you have to hit exact parts that are lined up with walls of sequenced backing tracks on point, every night, exactly the same way. If you screw up at all it'll jump out. But then, most pros have devoted their lives to playing at that level. You might hate Madonna, but check out videos of her eighties concerts, where she had guys like
Omar Hakim and Victor Bailey playing in her bands. Check it out, because by the time they get to around 6:00 they are absolutely killing it. I dunno - I've known a lot of dudes from that circuit and they get and keep the gigs because they nail it, spotless, night after night, and if you're singing backing vox you better be on-pitch, on-time, all-night. There's a reason why guys like Lee Sklar, Jimmy Johnson, Pino, etc., get all the gigs when they come up - they're pro and don't make mistakes. It's a totally different discipline than jazz or funk or jam based music, because...
3. If you're playing that stuff, who cares? You should be going for it and mistakes are gonna happen. It's all about how you recover and adjust. Half the time that's where the magic is anyway. That music is all about the moment, creating a unique experience or everyone in the room every night, so whatever's gonna happen is gonna happen, and it's all good.
Cause it's never happened to me before!!!
. This mostly happens in practice, on songs I am super comfy with. My mind will wander away from the task and then I might lose track of where in the song structure I am, etc. Live not as much since I am much more in the zone. 
