I think I'm slowly getting it...
(I WAS basically just thinking of a blog as a super-easy to manage website that basically comes with free website management software that prevents you from doing dumb things and I wasn't really thinking of the other social aspects in my mental definition.)
Thinking of my blog as my own individual forum on a message board, and thinking of the entire "blogosphere" as a giant, global, decentralized message board I think helps me think of it more accurately.
It definitely makes it less clear when to post on a discussion forum and when to post to a blog, but I think I get it (at least more than I did before).
(Not sure if I want all the hassle of a blog, or just a simple website to document static content now, but I do really appreciate all the feedback and everyone straightening me out.)
Adam