Quoting .Twat.Waffle.:" What are your views on this? I could understand if they are used basically as a daycare, then yes, ... [snip!] ... once a month so you could go to work or have a little time to yourself.... do you think they should still be paid for that?"
If they want to or ask to be, then yes. My family watch my kids and I do not pay them for it. They really want to and would never accept any form of payment for it. Likewise, I watch kids in the family because we're family and I'd never ask for payment.
However, as an aside I guess, you should bring what the kid needs too. As in, I have a sister for whom family watches her kids constantly. She never even would bring clothes or diapers or ANYTHING so the family has to supply everything for the kids.
I think a lot depends on the family. I don't think someone is out of line for wanting to be paid (they are taking their time to watch the kid as a favor), but at the same time few families I know would want, expect, or even accept payment for that.