From Ethereum's website (emphasis mine):
Using Ethereum, you can create a contract that will hold a contributor's money until any given date or goal is reached. Depending on the outcome, the funds will either be released to the project owners or safely returned back to the contributors. All of this is possible without requiring a centralized arbitrator, clearing house or having to trust anyone.
Taken literally, this of course is not possible. A toy example may have computationally verifiable goals, but almost all real projects have ambiguous goals. Who's to say whether a goal has been reached or not? Are contributors the eventual judges on that? In that case, doesn't the project owners need to trust the contributors?
Can someone explain the central idea behind this trust-less kickstarter concept?