Yesterday I expressed doubts about Jeff Jarvis’s view that the top 100 blogs get less traffic and links, and generate less interest than the bottom 7,999,900 blogs.

A few readers wrote me defending Jarvis’s observation. The long right-hand “tail” is where all the action is, they say. (If you don’t know what that means, skip the rest of this post; it probably won’t interest you.)

Never mind that it always seems to be the same half-dozen or so bloggers who get to go on TV and get quoted by Howard Kurtz. Jarvis’s defenders point out that if the 7,999,900 bottom-ranked blogs average only 1 visit per day, they get more visits than the top 100 blogs (which in the aggregate average a little over 2 million visits per day).

Well, okay, it’s hard to argue with that.

But dig a little deeper and you’ll find that many of those 8 million blogs aren’t active. Indeed, many seem to be computer-generated spam, not real blogs.

David Sifry of Technorati, which is the source of the 8 million blogs number, concedes that “there is a dark underbelly” to the numbers. He says Technorati removes about 90% of the spam blogs, but even so it is clear that quite a bit of spam remains.

Don’t take my word for it. Type the name of any commonly used spam term (“Vioxx,” “Viagra,” “mortgage,” “refinance,” “loan”) into Technorati and see what comes up.

Or just take a look at the last dozen or so trackbacks to this post. [Ed: Correction, 9:54 am, David Sifry informs me that trackback spam is not included in the Technorati index.]

Related:
- How many Americans read political blogs?
- Clay Shirky, Power Laws, Weblogs, and Inequality

Update: Sifry says 45 percent of blogs in Technorati’s index haven’t been updated within the past six months.