Zero-Knowledge Contingent Payment
It's unfortunate that most bitcoin-related posts require the reader to have a lot of in-depth knowledge about the details of how bitcoin transactions work. As somewhat-interested-person, I can /just/ figure out what the gist of the story is ('Alice can show she knows the answer and can then transfer the answer in an atomic payment'), but it's completely unclear to me how either part works. The "The buyer makes his payment to the following ScriptPubkey" section is maybe the worst offender in that respect -- apparently that script is supposed to be obvious, but it's not clear to me what it does /at all/.