I'm in two minds about this exercise. Part of me thinks it's just vacuous; people who like blogs like Iain Dale's like blogs like Iain's - whoda thunk?
Another part of me, though, thinks it's downright pernicious, in three senses.
First, those who know little about blogs - some dead tree writers, for example - might think the higher-ranked blogs are good representatives of blogging. And they'll be disappointed; most of them are empty-headed, dull and trivial wannabe dead-tree writers. This might turn people away from blogs, not realizing the riches they can offer.
I'm not making a partisan point here. Among just "right-wing" blogs, there's vastly more sign of intelligent life at, say, Matthew Sinclair, Mediocracy or Freeborn John than there is among more highly rated blogs.
Secondly, there's something nasty about the very notion that blogs can be ranked on a simple single ordering. The overwhelming virtue of the blogosphere is its diversity. And the many things that make a good blog are to some extent incompatible; originality versus consistency; passion versus intellectual rigour; number of posts versus quality of individual posts; brevity versus weight of evidence; wit versus gravitas, and so on.
These trade-offs mean the quality of blogs is just incommensurable - we can't rank them. I can't say whether I prefer Tim, Norm, Justin, Paulie or Damian or countless others. I like them all, in different ways.
And even if we can each rank our own preferences, what meaning is there to an aggregate ranking? To pretend there is one is to commit the error that libertarians have often accused utilitarians of making - of believing preferences can be easily aggregated when they cannot be. It's symptomatic of the intellectual decline of the Conservative party that one of its cheerleaders should make this error.
Thirdly, even if others' preferences can be ranked, so what? Why should I give a damn what others think? I don't blog so I can be judged by any middle-class moron who thinks his opinion matters - that's what I go to work for.