I've gotten a few offers to do a gig at a party, and then have it taken away on just a few days notice, and one time only one day's notice, because they decided on something else. Sometimes "We want this folk group for dinner music" really means "We want to have your name in the hopper but we're still looking." It's a pain in the butt, it shows no respect for the time and effort musicians put into preparation, and it leaves you feeling helplessy frustrated. People who do that just don't get it. It's a little different than what you're talking about here, but the same mentality.