Well, I started with the first post...
My blog has mostly benefited me in terms of finishing projects. I tend to be the "90% done... oooh, new shiny!" kind of person, and blog posts of finished projects helps cure me of that. I've met a few interesting people as a result, and have a corpus of "Hey, I know what I'm doing in a range of areas..." material out there, plus... oh, beer money, ish. I average about $40/mo, which is pennies an hour for the work that goes into it, but I learn new and interesting things.
My plan? "Post about things I was working on or found interesting." So far, so good!
But, in general, starting a blog with high expectations leads to disappointment.