In contrast, one can appear on the surface to be an altruistic blogger---writing about things rather than yourself---but still fall into the trap of narcissism, in this case, saying things about your topic because they pop into your head rather than because you think they'll aid your audience.
Thus, you could have a blogger who blogs for selfish reasons but blogs about the behaviour and affairs of a wide range of people because they are interested in other people. This is how I view myself: I blog because writing out my thoughts helps my crystallize my thinking and ultimately manifest changes in my own life and career. But while I blog about my own work I also blog about things I observe that interest me, and many of these things are concerned with other people.
That's my story and I'm sticking to it!
A blogger "spew[ing] whatever thoughts they had that day" just makes them a shitty writer. It doesn't matter why you're spewing them; if you write shoddily about arbitrary topics "for others", it doesn't make the blog any better. There's no need to do a bunch of categorization beyond that.
Most of the great blogs that I visit are all done altruistically. They are well maintained, post useful information, and very rarely waste my time. They also require a huge amount of effort on the part of the blogger because they really have to do work to gather and present interesting and useful information for their readers.
What a lot of the press has referred to as blogging is "narcissistic." Instead of coming up with interesting information and vetting it for their readers they mostly just spew whatever thoughts they had that day onto the page. It doesn't take a huge amount of effort, but the signal to noise ratio is also very low.
With the rise of Facebook and Twitter, narcissistic blogging can happen more in the sphere you want it (your friend group). Narcissistic bloggers are usually doing it for attention and their friends' and acquaintances' attention is more important than strangers'.
Altruistic bloggers, on the other hand, have useful information to present so they want to present it to as large an audience as possible. While I think we'll see more narcissistic bloggers moving to Facebook and Twitter in the future, hopefully the altruistic bloggers will continue putting the time in for the public.