I think it's just rude, to be honest. It's a way of saying "Look at me, I'm so busy and important that I don't have time to check my typing (or learn to use a spellchecker)". If someone wants me to do something for them but can't be bothered to take the extra minute necessary to re-read what they've written and make it make sense, why should I take the extra time to decode their message and do what they're asking?
no subject
Hear, hear.