Why aren't there more forum-blogs like LW?

The problem is that LessWrong runs on the Reddit platform.

That platform is in Python with some plugins that aren't easy to install. It's not like installing Wordpress on your Php based hosting.

The platform is also structured in a way that makes it hard to update the code in case of bugfixes because you have to make custom code change for your own website.

If you wanted a solution that get's widely used the best way would be to write a Wordpress plugin.

http://bleacherreport.com/ + http://www.huffingtonpost.com/ + http://seekingalpha.com/ are all part of the new wave of "forum blogs". They don't seem to take the LW approach of shaming people in to quality... instead, they seem to encourage the production of lots of content and then build filtration mechanisms on top of that. (IMHO, Less Wrong's moderation is overly harsh and just having upvote/downvote buttons gets you 80% of the way there without encouraging your users to use them. But, others have told me that they get REALLY PISSED OFF when they see things on Less Wrong that seem stupid, to the point where just a few persistently wrong regulars can turn them off the site completely. This is an outlook I have a hard time empathizing with.)

http://www.kuro5hin.org/

Kuro5hin has been around since the early days of the internet. There are other forum-blog hybrids out there as well. As for why they haven't taken over the internet, I think it takes a very specific type of topic and community for one to grow naturally. The forum-blog approach is well suited to applied philosophy, but I'm not sure what else.

One large difference yet to be mentioned is the existence of the sequences as a frame of reference.

There are forums with popular blog sections, e.g. teamliquid.net which also features a wiki. There are also forums that treat top level posts differently, e.g. by displaying them prominently at the top of each thread page. None of this is really new.

On the other hand, I feel that in some regards, LW is too different from traditional forums, like that threads are sorted by OP time rather than the time of the last reply, which makes it very difficult to have sustained discussions in these threads because they stay hot for a few days, but afterwards people simply stop replying, and at best you have two or three people continuing to post without anyone else reading what they write.

SETT is a way to create a similar framework that's easy to use.

What about Reddit?

please consider converting your blog into a forum-blog in the style of LW.

This strikes me as somewhat technically difficult: AFAIK, there's no equivalent of Wordpress for Reddit's source code.

I feel that this kind of forum-blogs can be very useful in many domains: math, physics

Are you aware of mathoverflow and physics stack exchange?

The unusualness of LW may be self-reinforcing. You start a forum, or a blog, and can count on people arriving to it knowing more or less what to expect based on other forums or blogs they've read, as appropriate. As a weird hybrid... honestly, I've was an Overcoming Bias reader before LW existed, and I still don't feel totally comfortable with the format. So that's a disincentive to create more weird hybrids.

Launching a neuroscience blog is on my to-do list - although it's currently in the idle-daydream-planning stage.

I, too, looked at Lesswrong's reddit-blog hybrid format and thought it was awesome and worth imitating. However, I don't have the technical skill make any forum let alone a reddit hybrid, nor do I have a good estimate concerning how long it would take to figure it out. I also don't have any idea how to deal with spam and stuff.

Here's an intermediate coding-noob friendly solution I've been considering, inspired by the existence of reddit.com/r/hpmor

Rather than a traditional comments section, you make a subreddit devoted to your blog. You post all blog posts on the subreddit. The "comments section" consists of a hyperlink to the subreddit post. If any of your readers have anything to say, they can post on the subreddit. You can take the high quality reader posts from the subreddit and transfer them to the main blog, giving the poster credit. Reddit does all of the anti-spam stuff for you, and you just piggyback off the service. It's a mutualistic relationship - reddit assists with forum infrastructure, and your readers will become redditors. If readers is important to you, you might even get a little traffic from users cross-posting your stuff to other subreddits.

Again, this is idle daydreaming on a topic for which I have no experience, so it's completely possible that this is a dumb idea. If you know what you are doing and idea strikes you as incredibly bad or incredibly good, please do let me know.

SBNation.com blogs are like that. The main people write the main blog posts but anyone can post 'fanshots' (really short posts) or 'fanposts' (longer posts) and if the blog bosses think a fanpost is really good they can move it to the main section.