Thanks. This makes sense, it is indeed a sort of legally binding agreement between a company and "the public". I'll note that despite the grandparent's flippant

Thanks. This makes sense, it is indeed a sort of legally binding agreement between a company and "the public". I'll note that despite the grandparent's flippant comment, this does not involve a "contract" or "written signatures". However, this kind of competition or prize is kind of the inverse of an oracle: The company says that they will give someone money for certain actions. The oracle is the inverse: It promises to perform certain actions for anyone who gives it money. In some sense I realized that there is a similarity to mail order catalogues, where you don't have a contract with the company before sending them money out of the blue. But is that the law that an actual court would apply to a random website that announces "we will provide accurate data about X to anyone who sends Y amount of Ether to address Z"? Possible. (But again, not a contract with "written signatures".)