A friend of mine wants to make some predictions about the future, but place them on a site where he can't edit or delete them after posting, to avoid accusations that he deleted bad predictions or edited predictions to be correct after the fact.
Is there a site that does this in general? I've seen some specifically for stock market predictions, and so on, but none for general predictions. I ask a similar question at https://quant.stackexchange.com/questions/774/keeping-a-track-record-honest but this is in some sense more general but also less strict: I don't need something that is cryptographically secure or will hold up in court- just a site with a general "no delete, no edit" policy.
I've offered to post my friend's predictions on my site, but I hardly qualify as a disinterested third party.