Just in terms of law: it's not an investment, it's not a purchase (since there's no guarantee of backers receiving their rewards), it's not a loan. It works exactly like when your local public radio station offers t-shirts to donors. IANAL but it seems pretty clear that kickstarter revenue would be a donation from a legal perspective.

As a backer, I'd treat Kickstarter just like setting the money on fire.

As a project, I'd be unlikely to offer a complicated physical device that I was not yet able to produce. I might put weaselly bullshit about a reward being a great sticker and up to 1 device.

I think the actual litigation that has already occurred -- e.g., the Washington State and FTC consumer protection suits -- have treated it mostly as a purchase (money exchange for a specific obligation), and certainly not as a donation.

It's certainly not portrayed as a pure donation (money given with no specific reciprocal commitment) in Kickstarter's terms.