No, not they are not a double-edged sword, they area a single-edged sword and they cut everyone - and the point of journalism - to ribbons.
If I could change anything about modern media, it would be to remove comments from news stories. Want them on features? Editorials? Okay, fine. But on actually news stories, no. If you, a reader, need to comment, then start a damn blog and have a field day. Comments represent faux-participation and empowerment at its worst. They also allow us to be lazy, ill-informed, gossip-mongering idiots.