Crowdfunding as a growth/marketing strategy?

Has anyone here had experience with crowdfunding? I recently started generating revenue for my startup and am not hurting for money, but a couple of my users have asked whether they could invest. That got me thinking, if I can get a few hundred or thousand of my users to invest, would that work as a marketing/growth engine? Many users have also asked whether we have a referral program, which I've said not yet. To be honest, I'm worried about a referral program backfiring because right now we're spreading through genuine word of mouth without any ulterior motives. I have this really crazy idea that maybe rather than us paying our users to refer others, we can make them pay us (in the form of investing), so they have skin in the game. Then there's no conflict of interest when they spread the word! And even if people do find out they're investors, it's actually a strong sign that they really believe in the product, rather than them just wanting to earn a few bucks on the referral.Thoughts? Is this a crazy idea or it a really normal reason to crowdfund that I just don't know yet?