One danger of articles consulted online rather than printed or downloaded: online articles can change their stories over time, and those updates can help the present control the past, or at least, control the report of the past. That can be used to correct errors, but also to surrepticiously modify undesirable information.
I corrected an example in my post about Markov's inequality, after a comment pointed out that it was wrong in one interpretation. Added a comment, but whoever reads the post but not the comments will never know. (I could also have deleted the comments to erase the past completely!) No big deal for scientific text, but more dicey for journalists writing about political events in online newspapers.
One partial solution: show your work by displaying text that has been modified. I just did that for the blog post on Israel and France sister countries, using strikeout text. I am rather pleased with the result: the factual error is corrected, but the previous version is still visible. I think that it is better than deletion and disappearance.
Should journalists do that when they modify an article after it's been published online?
How about moderators of popular blogs, should they do that? Rather than delete comments that they don't like, leave them in but strike them out? That would make their bias or objectivity evident, and thus make them accountable to the readers.