Awesome app! Constraining the time to 1 week makes users more interested. An MVP of anything can be built in ~4 days.

captcha is probably enough for spam control.

Posting it on /r/Crowdfunding might get more users.

I'd love to help when you're ready to build the first project :)

edit: If there aren't enough votes after a week, maybe try requiring some number of votes before the project gets built. 500? 10000? Something that will give enough time for the projects to get enough attention.