Consideration is a hard requirement for a binding contract. Note however that consideration in contract law doesn't mean the same thing as in general usage: in

Consideration is a hard requirement for a binding contract. Note however that consideration in contract law doesn't mean the same thing as in general usage: in contract law it means "something of value". So a contract promising to give someone a guitar is not enforceable, but a contract promising to sell a guitar for $100 is. In general the likelihood that the parties have read the contract doesn't have any bearing on the enforceability of it. But most such contracts are also contracts of adhesion (roughly speaking a take-it-or-leave-it offer), and there are special rules for the enforceability of contracts of adhesion. The principle is that they can't be too surprising or too unfair. There's a fair amount of case law about where that line is (which I mostly don't know).