On one level I think I'm sympathetic to Doug Johnson's "blogs : junk food :: books & journals : healthy food" analogy. I mean, I'm stuck a quarter of the way through a couple good nonfiction books, Anxious Parents: A History of Modern Childrearing In America and Off the Books: the Underground Economy of the Urban Poor, not to mention The Wealth of Networks, which is literally too thought provoking for me to read more than a couple pages at a time, or all four volumes of The Nature of Order, which will probably cause me to guiltily avert my gaze for decades.
However, the (nutritional) value of blogs varies by discipline. You can safely not read education blogs; they just aren't that good yet. And in my humble opinion, you can pretty safely not read anything being written today about educational technology.
On the other hand, if you're interested in web technologies, scripting languages, open source, XML, etc., you're well served reading blogs, and if you're not reading blogs, you're reading mailing lists, chatting on IRC, etc. You really don't need to read Communications of the ACM for this stuff. If you want to follow politics in the US, you should first and foremost be reading blogs; if you wanted to stay on top of the Libby trial, you needed to read Firedoglake.
But what really freaks me out about his post is the list of more nutritious alternatives he comes up with. It is all this political/institutional marketing crap reports from ETS, the Department of Ed, Educause, Cisco. I guess if you want to grow up to be a lobbyist or a librarian that's what you should have for breakfast, but it is pretty grim fare from my point of view. Even worse, grim and trendy.
When I read posts like this it is like I can hear the clock ticking in the writer's head... "We've been doing blogs for like two years now. Time to stick a fork in 'em and move on to The Next Big Ed-Tech Thing."