I actually spoke with the Kickstarter guys back in 2009 when I was considering branching off their idea specifically for product based ideas, thinking that it could be "Amazon for stuff that doesn't exist yet".
We all agreed that the idea should happen, but Kickstarter didn't want to do it for two reasons:
1. Their goal is to help artists succeed. They're artists themselves, and the guy who started the site's been working on this for years. It means a lot to them to help the little one-man filmmakers.
2. The risk in having products that aren't delivered on time, in the same form as envisioned, or aren't even completed was just too high. They were terrified of having a backlash of backers who thought they were purchasing a product when in fact the transaction is structured as a donation.
The second one is what makes me worried. What happens if, worst case scenario, Pebble goes bankrupt without producing any items? Who takes the hit there? Is it Amazon, Pebble, Kickstarter, or the backers? It isn't clear yet because we haven't had a high-profile failure yet. But it's only a matter of time.