If we stick with the strict contract analogy, we might also run afoul the concept that illegal acts included within the contract nullify the contract. I'm not sure if gambling using one's signature as the consideration is technically illegal or not, but in some state, I'm sure it probably is (and since this is the internet, defining the situs of the contract is probably subject to any number of interpretations).
I only post this bit, BR, because I was going through the exact same thought process you were, and the stuff above was part of the little theoretical stuff I had going on in my head.
I also believe one person claimed to be drunk, but I remember a case from my business law class from back in the day where it was ruled that being drunk doesn't invalidate a contract, even if it is a really bad contract. I don't know what impact that would have on things.
In the end, though, there's a lesson to be learned. If you want people to honor the intent of your written agreements, make sure your written agreements don't say the exact opposite of what you intended them to say.
