Neither one of these is compelling to me as you have to prove that this was the only prediction you made and you aren't cherry picking the correct ones.
Goes back to an old stock prediction scam. You choose 1024 and send 512 the prediction that a stock will go up and 512 the prediction that the same stock will go down. Each day you repeat this process only with the group where you were right. So, 512 -> 256 -> 128 -> 64 -> 32. Eventually you have a small number of people that think you can predict the future and you can ask them for money that you will invest on their behalf.
This also happens in the sports betting world. People use this method to convince others that they can consistently predict the outcome of games, or the spread, or the other stuff people want to bet on.
Preventing one individual from making multiple predictions doesn't necessarily solve this problem. You can do the same thing by getting 1024 people together to make a variety of predictions. At the end, one person looks prescient.
It's not clear to me how any system (other than education, which is obviously a very different topic) can solve the gullibility of people who are uneducated about basic game theory and common scams.
