I think I see where you're coming from. I was recently thinking of starting up a technical blog as a form of self-promotion and to have something to show to potential employers. But I also wanted to do something that I felt was good and worthwhile to readers. So I thought about the sorts of programming blogs I'd read in the past that I could maybe emulate or use as a standard. And then it occurred to me that, for the most part, they're either a waste of time, not terribly interesting, or even harmful. I've had better luck with reading textbooks, though maybe I just prefer to try and learn a subject in some depth. But when what you're really selling is your knowledge and expertise, I can see why people do it.