How is Kickstarter any different than me paying an artist to write a song for me on my behalf or a carpenter to build me a house?
I'd certainly have ground to sue the artist or carpenter if they failed to eventually deliver a song or house (or indeed, didn't deliver one according to the terms of our agreement).
I think those are bad examples for the typical / canonical crowd funding campaign, because those are examples of craftspersons producing yet another of a well known product. The craftsperson can be judged on their past works, and they can accurately judge the cost to do it again.
The ideal kick starter is more like a trading expedition in days of old. They are proposing to set sail for distant shores and bring back untold riches, but a lot could go wrong along the way. The ship could sink, the lands they reach may have no goods for trade, the locals might not be interested in the goods the explorers brought, trade goods they do acquire could spoil on the way back... this is not fraud, this is risk shared by the backers. If you don't want risk, invest in T-bills and buy goods in physical stores.
Because you're funding a project that may or may not work out. The whole point of crowdfunding is supposed to be, "You give us money to develop an idea, and you might get a reward in return", not, "I'm paying you $35 for an order that includes a bumper sticker and a t-shirt with your logo on it." It's less like your carpenter example, and more like a VC firm dumping money into a startup.
It's supposed to be speculative investment. Whether or not Kickstarter and others have decided to backpedal and pretend they have some kind of legal precedent for holding project owners to their word, in order to make their own business seem more legitimate than it is, is another story.
There's no requirement that the Kickstarter complete the core project - just that they provide any promised reward.
Many projects, where the project is highly speculative, provide explicit rewards and then an offer to get the benefits of the main project that's conditional.
Also, in what way is it not like an experimental house design using, eg, 3d printed concrete (in some new manner)?
There's a well established body of contract law about how to handle that kind of contract to build a house with a new technology, and the liabilities involved.
There's no requirement that the Kickstarter complete the core project - just that they provide any promised reward.
That makes no sense. Much of the time, the reward is directly related to the core project.
Also, in what way is it not like an experimental house design using, eg, 3d printed concrete (in some new manner)?
I'll repeat myself - I have no idea what model Kickstarter is now framing themselves under or how it applies to the legal system, but in the original model for crowdfunding in general, you were giving a voluntary donation to an idea with the explicit knowledge that you might never receive it or any associated awards if the project failed. You weren't paying for a t-shirt - you were giving money to someone's business/creative idea and receiving a "free" t-shirt in return.
What Kickstarter's Terms of Use, then and now, actually imply and signify in a legal sense, and whether or not the defendant can easily make the claim that risk was fundamental to nature of Kickstarter project backing and thus the backers voluntarily chose to engage in a speculative transaction which had no legal obligation to be fulfilled, are questions for an attorney to answer.
Do I think the guy cut and ran? Yeah. Do I think that's wrong? Yeah. But I also think if it was made completely clear to each and every person donating that what they were doing was contributing to a project, not making a purchase (Kickstarter even states themselves that they are not a store here: https://www.kickstarter.com/blog/kickstarter-is-not-a-store), then enacting Consumer Protection borders on protecting people from their own stupidity.
This is specifically not one of the Kickstarter backers suing for breach of contract, though. This is the state attorney general bringing a prosecution for violation of consumer-protection laws, which is a different legal situation.
I'd certainly have ground to sue the artist or carpenter if they failed to eventually deliver a song or house (or indeed, didn't deliver one according to the terms of our agreement).