They do promote. Many people browse the site, receive emails, etc. Kickstarter makes a point to put in the creator's dashboard a pie chart that shows how much t

They do promote. Many people browse the site, receive emails, etc. Kickstarter makes a point to put in the creator's dashboard a pie chart that shows how much their promotion has brought in vs. other means. In my experience their slice is between 25-50% (skewing smaller as projects are more popular).