Young artists, in their excitement about a new project or idea, can't quite make the distinction between "I want to," "I intend to," and "I will" -- and the relation to reality that each of those has. They'll say, "I will do [shiny thing]!" when what's actually the case is "I want to do [shiny thing] and currently intend to do [shiny thing]." However, somewhere between "I want" and "completion," the young artist falls deeply in love with [NEW shiny thing!] and their plans get knocked all askew. They still love [shiny thing] and in some fantasyland of their brain where the rules governing reality can be bent at will, they still intend to do [shiny thing], but that has taken second place to the overriding passion they feel for [NEW shiny thing]. The problem is, there will always be another [NEW shiny thing] ready to jump in and knock the current one off its throne.
That fantasyland is very important, mind you. It's one of the essential things that makes a creative type able to create. So don't think I'm dissing it. But it is a fantasyland, and one of the thing every artist needs to learn is how to live in reality and go visit fantasyland -- while still being able to come back.
Over the years, and with no small amount of difficulty, I've learned to do this. I've become very good at only taking on projects that I know I'll be able to follow through on in reality, whether it's writing X amount of words every day, doing Y number of badges at a con, or whatever. However, I also learned to keep in mind when working with other creative types, that many of them are still fighting with that particular demon, and that you have to learn with each individual, just how much stock to put into their use of "I want to," "I intend to," and "I will," respectively.
Some are solid as a rock -- Vince Suzukawa springs to mind here as somebody who absolutely delivers if he's agreed to something. Some are a little more wobbly but will keep their focus with repeated gentle prodding. Others (and no, I'm not going to name names) are completely out in space and you can't believe a thing they tell you -- not because they're trying to deceive you, but because they don't have the self-discipline to turn "I want" into "I will."
Every artist I've ever met had every intention of following a project through to its completion; at least one took $250 up front, never delivered, promised they would refund the money, and then never did that, either. The person wasn't a scammer -- they had done beautiful work for people before -- they just couldn't keep their focus. I eventually stopped chasing after the money because it would take litigation to get it back, and that would have cost me more in the long run. But it did make me more wary of working with other artists later -- as well as making me a lot more cautious about maintaining the integrity of my own reputation.
So what am I getting at, here? Just this -- I hear a lot of horror stories from both artists and buyers about flakery, and it is a real problem. However, it's a problem that's endemic, and the only real protection from it is your own precautions. Art is like gambling. If you're a buyer, don't offer up money you can't afford to lose; if you're an artist, don't start a project until you're satisfied both that the buyer really will pay, and that you both can and will finish the job -- and if they buyer doesn't pay, that the loss of that expected income won't cripple you.