I think the blogging world has come a long way since the hayday of Xanga and LiveJournal (which, for me, was circa late 90s). I think you hit the nail on the head for a lot of people, because an unfiltered view of our inner-most thoughts -- archived for all eternity -- isn't necessarily complimentary to the notion of, say, convincing an employer that you're worth hiring. I use an alt for any sort of ranting or not-necessarily-mainstream opinions, and I go to great lengths to keep it completely isolated from my floor9 and blogHarrisburg personas.
I also don't buy into the whole "Twitter is dead" movement. Twitter is rocketing towards mass abandonment, at which point it WILL be dead, but it hasn't gotten there yet.