Yeah, I definitely agree that this should be the case. Also, perhaps we should keep a record for all the previous edit histories, so that if someone attempts to cover up evidence, we could just dig up the archive?
I guess that would be a reasonable idear, altough it's a two sided sword: I already posted private information once (something that could be used to identify me), and i was very happy that i could just edit the post and remove this info.
Maybe it would be sufficient if everybody knew all edits were kept in the database, so if evidence was ever needed, theymos could potentially dig it up.