I've seen that on a lot blogs, but never thought about where it came from.
I know of some others about depression, alienation and things like that...
Most things Nananan Kiriko has written Oyasumi Punpun
The main character might throw you off, but it's a very sensitively written
Some examples: OneTwo
I am fond of Hyperbole and a Half. The "simple dog" posts sometimes pop into my mind randomly and then I start giggling, seemingly out of nowhere (to the rest of the world).