I've considered something like an electronic notary system a number of times over the years. I can imagine having a URL like http://[known http://[known and tr

I've considered something like an electronic notary system a number of times over the years. I can imagine having a URL like http://[known http://[known and trusted e-notary].com/[user]/[date]/[file or md5sum] would do a lot to discourage any shennanigans. It wouldn't serve the same purpose as having something actually notarized so you'd have to be clear about that, but it could be a source of evidence when a case went before a court. Doesn't seem all that technically difficult - md5sums for files and an RSA keypair per day are the common starting points for most of my ideas in that direction.