That is one of the main reasons to own your own data and not to trust some company with it. Just post it on your own blog and link to it instead.
Doesn't this ignore the power of having a common place to go for questions and answers, back and forth, etc.? I visit a couple of sites almost every day, and (I hope) help as well as be one of the people helped. But I'm not googling extensively for newly-posted things every day.
Say you find a bug with Product X v1, create a workaround, and post it to your blog. In V2, the problem has been fixed, or exists in a slightly different incarnation with a slightly different workaround that someone figures out only after reading your content. Maybe they'll leave a comment on your blog about it, but you don't really have any incentive to update it. If your post was an SO question, they could post another answer or make an edit, and the page becomes the canonical source for information about the bug.
How many times has HN discussed the digg/reddit/HN decline in quality as the population grows?
In their minds (and I have to give them the benefit of the doubt given their awesome accomplishment!), keeping strictly on topic is one way to prevent the point of the site from drifting.
It may be that the SO people "want" is a better one. But that's the decision that Atwood & co. have made. To wish for a SO that allowed off topic responses is to ask for a different product.