It's an axiom of Web 2.0 that you have to, have to allow users to comment on your content. Have to.

And there's no question it can lead to some interesting, provocative, productive conversations. The downside is that it can also lead to little more than splenetic venting.

Drop by any CBC News story on, say, a crime, and by far the most common comments are people who have nothing to add except anger and demands for vengeance. Oh, and off-the-cuff diagnoses like "he's clearly a sociopath." That, friends, is the kind of high-quality psychiatric analysis you just don't get from news outlets that don't allow comments.

News sites in particular are bedevilled with facile grievance-airing and axe-grinding, often in hostile and polarizing terms. Maybe there's a therapeutic value in all this mouthing off... but it comes at a pretty high cost to the rest of us who read it and recoil, repelled (and in need of some kind of karmic bath). It also means that anyone who wants to have a meaningful conversation about important public issues is probably going to go somewhere else.

(An interesting wrinkle: the conversation on the CBC News blogs is often very civilized - maybe because they're less prominent.)

Comments are very Web 2.0, but just tacking them onto any old content isn't going to necessarily spark scintillating conversation. You need to think carefully about both your audience and your intentions. The Tyee undertook a major initiative to improve the often-toxic conversations on their site; they've made real progress despite some early skepticism. (Full disclosure: we worked with them toward the end of that process.)

Sites like the CBC are missing an opportunity to host a productive, positive exchange of ideas. (It's especially unfortunate because the CBC has done such a great job in other areas, like podcasting.)

Instead, they're just giving voice to our collective id... and it's not pretty.