What happens when the Kickstarter project DOES get funded, the person(s) behind it get the money to do the project - and then they don't follow through? Does Kickstarter refund my pledge or provide some sort of security or guarantee?
No. Kickstarter have no liability to you. According to the wikipedia entry, your only recourse is through civil court.
Kickstarter do take verification details from people proposing projects, which helps prevent criminal fraud. This can help you effect a civil claim. But they won't give you your money back or take action on your behalf.