[DarkShikari]

Banning IPs works well enough even for vastly bigger sites like Wikipedia. Combined with an open proxy checker, it's surprisingly effective.

It's not perfect, but for ANY site of sufficient size with unmoderated user content, this problem eventually has to be dealt with. Threatening to ban the victims is not a solution.

Kickstarter earns 5% from every single successful project: they can afford putting some effort into moderation and protecting their customers.