Crowdfunding works because you already know you are helping bring on a cool product that would not exist otherwise (and are aware of the risk that it might not pan out anyways).
Being asked politely and in an upfront way makes all the difference.
I used to be similarly uncomfortable about the "publish a fake product before you've actually built it" tactic. But I've since signed up for 3 products that didn't actually exist at the time - DropBox, RescueTime, and some analytics SaaS done by ex-Googlers - and each time my emotion was more mild annoyance rather than harsh anger. Heck, there's a whole industry (crowdfunding) now based around the idea of selling a product that doesn't exist yet and then using the money to fund development & manufacturing.
This is also not a new tactic - in the 80s, it was common for enterprise software companies to find an initial company, sell them the product, and then use the money to build the product. Microsoft did this with DOS - they sold IBM an operating system that didn't exist and then used the money to find someone who had written an OS for the 8088 and buy it from them.