37signals blog (Signal vs Noise) precedes Basecamp by a couple of years, their first post is from December 2002, http://37signals.com/svn/archives/000001.php. It was a pretty popular blog by the time they launched Basecamp.

Joel on Software precedes FogBugz, if memory serves me well. StackOverflow precedes Coding Horror, of course. The lesson here is that building a reputation comes very handy when creating web apps.

I think the coding horror blog benefited a bit in average post quality when Jeff switched focus to be primarily a developer/ project manager on stackoverflow rather than primarily a blogger. Previous to that while there was a lot of good information there, a lot of the posts felt forced, like trying to hit a quota, kinda like techcrunch.

I wrote the post mainly from an online tool perspective. Yes, Joel on Software and Coding Horror were very targeted as well, I didn't use them an example only because they belong more to the community camp.

I don't have much to contribute to this discussion myself, but from what I've heard/read, at the beginning, you should target other entrepreneurs/early adopters and when you get some coverage/traction, move to your target audience for your product.

PS: I'm really interested with what you guys have to say about that.

It depends what you are trying to achieve with a blog a bit to, are you trying to address customers, prospective customers primarily or are you trying to become an authority in your niche by writing about it more broadly and picking up a lot of search traffic. I think a great example for authority is SEOMoz, provides value well beyond the actual product.