in my experienceToday, Engadget, the king of gadget blogs, turned off comments site-wide. I did the same thing here a while back due to spam reasons, but Engadget has done so due to "mean, ugly, pointless, and frankly threatening" comments posted on the site. User and community involvement is a double edged sword, and I have to say, that on my own site, I miss seeing and reading the comments from my readers (I never had very many, but they were loyal).
So, what to do with comments on blogs? You'll never escape spam nor offensive comments, but there are ways to manage the issue...
I'll be watching what Engadget does since they are a part of a much larger network of blogs and there has to be a better way to do this (or at least a way that allows for comments that doesn't totally suck).