I've posted while intoxicated plenty of times. It's just that when I do, I have more to say than just "I'm durnk lolz." Also, Gebohq makes a good point, altered states can sometimes have beneficial effects on creativity (insert the quote here about junky musicians and anti-drug people who enjoy their music).
Then again, it can also just produce junk. Like Ginsberg said in Howl (paraphrased) - "[they] rocked and rolled all night over lofty incantations that in the yellow light of morning were stanzas of gibberish." I've had plenty of results like that too, it's a mixed bag.