1) The investigative blog
Searching for administrative errors and exposing 'cover-ups'; this is the category EU Referendum fits into. These are always going to be rare: investigative journalism is, as DK points out, a time consuming affair which many amateurs just do not have the time for. Equally, it is not an overriding priority for blogging: most of these discoveries are of minority interest and will not change the already existing public perception that the EU is a bit venal and the war in Afghanistan is not going great. Investigative work is worthy pressure on military and political leadership which is a decent way to spend one's time but is not important to the exclusion of the kind of political debate upon which governments rise and fall.
2) The analysis blog
This is the type of blog that mine aspires to be but the finest, and purest, example is the Becker-Posner blog. While there are few blogs which are as pure examples of this kind of approach as the Becker-Posner high minded effort they are certainly more common in the US than here. Their primary contribution is to regularly present some, hopefully interesting, new analysis of existing knowledge and contribute to the debate over its significance. They are usually less immediately topical than rapid reaction blogs and have a less adversarial approach.
3) The rapid reaction blog
This is the most populous category; the swearbloggers and the Daily Kos are examples of rapid reaction blogs. They will usually be the first to respond to new arguments presented by their opponents and will often also contain the most broadly resonant rebuttal. These blogs are important as they mean that the Toynbees of this world do not go unchallenged but for the rare occasions when some other columnist deigns to intervene. They are the lifeblood of the new debate which shapes thinking democratic opinion.
4) The gossip blog
This is the category Iain Dale and Guido's blogs fit into. Just because they are focussed on people instead of issues does not make them cheap. In a representative democracy issues of personality and interests are important. As we are electing someone to represent us for a period of years in which they can do largely as they please it is important that we know they are upstanding people so that when issues come up, as they always do, for which there is no prescription in the manifesto they will respond appropriately.
5) The round up blog
Examples of this are the ConservativeHome frontpage and Instapundit. There do not need to be many of these blogs but a good one is a huge asset to the community they serve. Their primary function is to highlight good stuff in the rest of the blogosphere and the mainstream media.
Of course most blogs are a mix but the important thing to note from this analysis is that all good blogs do not and should not look the same. Becker-Posner and Devil's Kitchen are polar opposites but both enrich the political debate. Richard North does not have the handle he thinks he does on what the blogosphere and media should consist of.
One final point, this was in the EU Referendum blog of a few days ago:
Conspiracy or carelessness? A vicious desire to do down the West or merely an ignorant and nasty desire to break up everything of value? Whichever it is, the BBC, the Guardian and the New York Times, together with their acolytes and followers can take responsibility for the murder of Sister Leonella Sgorbati.
This is both based on incredibly spurious research (that the BBC and the Guardian reported growing Muslim anger before it became obvious to the rest of us is hardly surprising from major news sources and does not indicate they imagined it) and shows a deep lack of moral sense. Anyone who blames those who report early incidents of rioting for someone murdering on the basis of a slight to their faith clearly doesn't have the right to lecture us about our immorality. If you kill someone because you heard about an insult to your faith that does not make the person who told you that insult occured a murderer. EU Referendum's search for conspiracy and media chicanery has led it to lose sight of even the slightest notion of what real responsibility means.