G'day Steve,
Actually I don't think we have a problem with people editing articles even if they do have a conflict of interest. It's better if they declare that conflict, of course. People editing articles about *themselves* seems to cause the most problems though, because they take changes so personally, and insist that they know themselves better than any published source could...
Of course, we also see it going the other way. A person's article is wrong, or concentrates too much on the trivial (e.g. Ian McKellan's sexuality), or is insulting. Someone comes along and fixes it, and gets reverted: "WP:AUTO! You vandal!"
And then you get people who'll insist that an article MUST remain the way it is simply because its subject doesn't want it to. People who just want to send a big "FUCK YOU" to anyone who would dare --- dare! --- criticise a Wikipedia article. Imagine if Seigenthaler had shown up and really *did* remove the defamatory sentence from his article, only to be reverted and blocked --- "don't edit your own article! Vandal!"
Moderation in all things. Ask Jimmy Wales what it's like to have an inaccurate bio of yourself on Wikipedia. Ask Chip Berlet what it's like to have most of your bio written by conspiracy nuts. I've never been notable enough for an article and (God willing) never will be, but if I were, I don't think there'd be anything wrong with stepping in to defend my own bio from vandalism and the rantings of fuckwits.