I'm possibly drawing to fine a distinction here, I'm not sure. There's a bit of ... flurry, around Amanda Palmer not paying her backup band. And it's an odd one. On the one hand, musicians definitely deserve to get paid. The whole "do it for the exposure" thing is complete bollocks.
On the other hand, when Amanda Palmers kickstarter was wildly successful, she did lay out where all the money was going, demonstrating quite well, I thought, how much it actually costs to put together a record and a world tour. In other words, she might have raised 1.2 million dollars, but she is by no means going to get rich off that, so calling her a stingy moneybags is not ... accurate.
The distinction that I'm attempting to make here is that when artists get asked to do it for the exposure, it's asking for a service to be provided for free. In this case, having followed Amanda for a while, I'm guessing that she's asked for volunteers and said that there's no money in it. Even without volunteers though, she would still play and the show would probably be grand. The concert tickets were iirc, part of the kickstarter rewards - so everyone already knows where the money has gone for that. So in the end, the service that was contracted (via kickstarter) will be provided, with or without a volunteer backup band.
It's a tricky question. One I'm at the moment going to, tentatively, come down on Palmers side on. She has built up a lot of trust with her fans over the years, I just don't see her squandering it like this. I could be wrong though.