It's up to you whether or not you want to do work with no contract. I think artists do need to do work with no contract, because what we're motivated by is not money. We're motivated by a need to express ourselves and to get our ideas out. That's the motivation. It turns out that when people like it they frequently will support you if you give them a means, but this is not a contract.
-- Nina Paley (3 May 1968-), American cartoonist, animator, and free culture activist, Youtube video "Copying Is Not Theft: Against Copyright Tyranny", 25 March 2011