At least in the US it still counts as a contract, and has been enforced in court. That is also a very fringe exception though.
I’ve made comment about the Kickstarter Terms of Use Agreement before in another thread, specifically about that “seller” unilaterally refunding a “buyers” money, and as it was in that case, to curtail negative comments from that buyer.
TheTerms of Use Agreement at Kickstarter is a challenge to understand, and at points in my opinion, should be made better, but still worth understanding if you are investing a significant amount of money. Other crowdfunding sites are more balanced between buyer and seller, imo.