I first have to take issue with his factual premise. On the right alone there are the Adam Smith Institute (probably the best developed), Civitas, the TaxPayers' Alliance and the Social Affairs Unit blogs. Others don't but, all in all, I'd say that over half of right-wing think tanks have blogs. My impression is that the left blogs somewhat less but there are still plenty of left-wing think tank blogs. That all these organisations are so keen to get involved in blogging suggests to me that the problem isn't, as Sunny suggests, some fear that bloggers will find them out. By putting their research out into the mainstream media they place it in the bloggers' firing line anyway.
So, most of these organisations do blog. What they don't do is interact with the blogosphere much. They can certainly work harder to make their blogs more involving with richer and more varied content. However, I suspect that the real difficulty has something to do with the rapid reaction/gossip focus in the blogosphere that Gracchi discusses. There are relatively few blogs demonstrating the depth of thought of, for an example you might not have heard of, The American Scene in the States. Our blogs are dominated by people expressing their immediate reaction to something they saw in the news. This doesn't take a lot of research, thinking or specialist knowledge to do well so the policy sphere loses its comparative advantage and becomes one more, often rather tame thanks to the need to avoid embarassing the institution, voice in the crowd.
This is not really something I'm inclined to get too worked up about. Blogs are written in people's spare time and the time and attention required for analytical work is a scarce resource. Getting too dissapointed that the product of amateurs writing with very limited time and largely for their own amusement isn't producing Dostoyevsky just seems unrealistic. In the States there is an interesting debate going on about whether Greg Mankiw, an economist with a serious academic reputation who does blog, can sustain that effort and whether he should.
First Dani Rodrik suggested that the best writers are the ones with the highest opportunity costs to their time blogging:
"So if economists with high opportunity costs of time start to get out, shall we have a lemons problem on our hands? Will eventually the only prolific bloggers remain the ones that are not worth reading?"
Blogging has very low entry costs but relatively low rewards relative to other ways someone with novel and interesting perspectives to share can express themselves. Iain Dale advised that the blogs further down his rankings needed to work on increasing their readership. If I write a report that gets covered in the Sun or makes the front-page of the Metro I reckon it will, in number of readers, achieve more than even the biggest blog can in months if not years. Look at the media coverage that the capital projects report got, if I'm interested in readership why should I bother blogging?
Perhaps we blog for irrational reasons, Nicholas Carr suggests some:
"But what's left out of all these economic equations is the ego-gratification that comes from being a popular blogger. Because blogging is such a personal pursuit, with strong and immediate ego-rewards, it can be irrationally seductive, particularly to highly competitive overachievers. The hazard - and this applies as well to disciplines beyond economics - is that extraordinarily talented individuals may end up, like lab mice drinking sugar water, spending more time blogging than they should, even though their comparative advantage is smaller in blogging than it is elsewhere. Distorted by noneconomic but nonetheless powerful rewards, the idea market would become less efficient than it should be, and we'd all suffer as a result. The real danger, in other words, may not be that the "lemons" - the "tolerable bloggers" - will take over as the mainstays of the blogosphere but that they won't."
Seth Finkelstein suggests some more reasons why people will over-blog in the comments:
"1) The lottery-like nature of the success argument.
Lotteries have negative expected value. This is very obvious. But people don't make good expected-value calculations overall (the ones that do, don't play lotteries!). This is apparent in the common evangelism marketing represented by the part about "actively demonstrating one's skillset for an interested public". There are very few winners in that game. But an unlimited number of aspirants can be induced to buy a (losing) blog-ticket in hopes of becoming one of the lucky few.
2) The objects-in-mirror-are-smaller-than-they-appear
It's really easy to think that your blog is far more influential that it is. A niche celebrity will attract enough of an audience to seem impressive, even though objectively, it's likely not. But still, you can readily get the impression it's more effective than rationally justified.
3) Random reinforcement
The occasional high-attention hit is great for misleading the blogger that they matter."
I only mention all this to illustrate how uncertain it is that analytical thinkers should get actively involved in the blogosphere. Perhaps those who do so now are essentially acting irrationally. Neither Gracchi nor Sunny ask the simple question, why should someone with interesting and novel things to say use the blogosphere as a medium? What is in it for them?
I'd suggest a few answers:
1) Anonymity - some people can only write on a broad range of topics with the cloak of anonymity or risk endangering their careers.
2) A place for ideas that are interesting but not worth the greater effort of preparing them for publication in another medium with greater rewards but higher standards. The blogosphere provides a small but significant reward for the presentation of ideas that aren't yet ready, are of interest to too small a niche or are not sufficiently novel for the big time.
3) A testing ground for incomplete ideas and arguments. If you have ideas that you are unsure of then dicussion in the blogosphere can either confirm that they are interesting and stand up to scrutiny or can reveal where more thinking/research is needed.
1) is significant but pretty constant. I think 2) is the reason most think tanks blog now. 3) probably has the most potential to encourage intellectually significant blogging. What is interesting about 3) is that it relies very heavily on a network. Blogs are most valuable when you are interacting with other bloggers who can challenge you and provide social rewards for your most interesting efforts in exactly the same way that a phone is most valuable when there are plenty of other people to call.
That might explain why it is difficult to get an analytical blogosphere going. I reckon lots of smart people start blogging and don't find it rewarding because they don't get into a community whose praise and criticism can make it worthwhile. That community is what those of us who want to see a more thoughtful blogosphere should all try to build.