Part of it is that too much concrit, especially when it's publicly offered, is neither constructive or even critical, if by that word we mean something judged and measured.

I think a lot of people do misunderstand what "constructive" means. As I said above, to be constructive you must first make an effort to understand the intent. Most people, myself included, don't make that effort when casually reading.

But even bad concrit can be useful. It's great to get an ego stroke and I wouldn't be without it, but someone pointing out what I've done wrong is just as great. I figure if someone cares enough to say it, there's an implied compliment even in the criticism.