Kickstarter is such a gamble for the donor -- you pledge your support, and then it's up to the author to produce something that you hopefully find worthwhile. There's no accountability -- I could die, or skive off with the funds, and you would get nothing. The former case is true of any pre-ordered book, I suppose; the latter, well, people make a judgement call on whether they trust the author to follow through. If the author doesn't, their reputation takes a big hit, and crowdfunding depends in large part on reputation. It's a whuffie-economy, to borrow a Cory Doctorow phrase. :-) I'll try not to let you guys down.
On the plus side, you get to help make something happen, that might not have happened otherwise. Hopefully something cool!