I don't mind the OCCASIONAL fuck up on a blog, because for the most part it's just some random dude spitting stream of consciousness style out to the universe. They don't have editors, etc. Plus, not everyone has mastered the skill of watching the screen while they type- lots of people still have to look at the fucking keyboard.
Pretty much anything else is infuriating, though. I hate people who are lazy about it, too- "oh i just cant spel" and shit like that. It's like, motherfucker, LEARN.