Hm...I am a big fan of correct grammar and spelling, if only because when I read a particularly muddled post it just smacks of laziness, and the author's point (however valid or interesting) is lost in a sea of 'alot', 'your' (for you're) and misplaced commas and apostrophes.
Having said that, it's up to the individual to make the effort to improve themselves and show people the courtesy of communicating clearly - I'm not going to police it.
Having said that, although I might personally capitalise my I's, I think the Internet has desensitised me to that one a little bit, so I don't tend to notice it so much. But 'your' for 'you're' makes me feel funny. =P