I have been donating on Kickstarter since their beta first launched and I too have considered using it for start-up investment, however...
First up, they use Amazon for the payment system which whilst allows investors from any where around the globe, projects can only be started by U.S users (At least users with U.S bank accounts anyway). As I am in the UK I couldn't raise funds with Kickstarter even if I wanted to.
Second, as Roland mentioned it really has been aimed at creative community, arty type projects. Some may turn a profit in the future but most are non-profit projects and ideas. This doesn't mean you couldn't try it (I would love to!) but I think you would be relying entirely on the investors you are able to drive to the site yourself as the current community may well be turned of by "business" start-ups. That being said, I have personally donated to three indie comic book creators through Kickstarter simply because of the chance it gave me to get limited edition and original products that I am interested in.
Third, you can not just offer up equity on a public forum like Kickstarter. Any investor must first be declared an intelligent investor (Or what ever the correct term is :)).
Actually, I have thought this could be a great possibility for someone to fill with a business type alternative to Kickstarter. After looking into the possibility the business I was involved in at the time meant all side interests had to be put away for another day. I did discover there are already some sites out there but I would keep it simple and stick to encouraging start-ups to offer creative rewards, memberships, access and products rather than mess with a really out dated investment law.
