Ask HN: How important are terms and conditions?

A lot of websites seem to have "terms-and-conditions" upon getting an account. How important is it to have them? Many of these are very verbose, and I don't know anyone who actually reads them. Is it possible to get away with a simple set terms such as: -> You are limited to one account per person. -> We will send you a cheque if you have earned more than $50. If you have earned below this amount, we are not obligated to pay you. -> You, or we may choose to cancel your account at any time, without reason.

Thanks for your opinions.