Yet database logs would also show when the words were changed even if a record of the original words was wiped out. Plus many internet blogs get cached on various search engines in their original forms. A government can, with enormous resources disguise all traces of database tom foolery; but I suspect what they would rather do more efficiently is to simply make things up out of whole cloth and pin them on a political adversary as opposed to messing with a database. Messing with a database means that computer forensics can show that the data were manipulated which can backfire on a prosecution case. If you make something up out of whole cloth complete with timestamps, then a defendent would have a much harder time dealing with trumped up charges!
It doesn’t take the power of the government to tamper with a database log. I assure you that when I said I could alter the post, I also meant the logs. It is a bit stickier with wiki’s since they usually purposefully maintain all updates. In the case of the wiki you have the database log AND the wiki records recording the update, but I know that it can certainly be done by a sysadmin with moderate database skills; e.g. myself.
[I am a computer expert. I do not play one on TV! :]