As I was replacing one word with a better one in my previous post this morning, it occurred to me that it's far too easy to change stuff on the internet with no notice. If I'm changing something substantive, I'll note it in an update or comment. I do edit without notice to improve the writing. But others don't necessarily do that.
I follow Ivan Oransky on Twitter (@ivanoransky). He keeps track in his blog of articles in scientific journals that have been retracted and related matters. Most scientific journals still have a dead-tree edition, so they have to be explicit about their changes. The downside of dead-tree is that the retraction isn't attached to the article, although careful searching in the conventional ways for this sort of thing should find the retraction.
Oransky has pointed out the sneaky way that popular media have changed some of their articles on the Web without any comment or update. Seth Mnookin has been following the misinformation about vaccines and autism in the same way; here's one example.
I've seen some of my critical comments disappear from others' Facebook updates. I'll bet there was a blog post that disappeared today after my criticism of it on a listserv.
In all those little ways, history is being rewritten. Some matter and some don't. But the culprits are not the ones identified in 1984, nor by the Tea Party.