Maybe you've heard about the trend of youngsters who are now using keyboard-equipped smartphones taking the trouble to type their words and grammar correctly, to show off their phones and their writing prowess.
Resorting to textspeak is lazy and suggestive of a lack of education, and that is not lost on those who have to read it. Sure, if you're back-and-forthing about your latest school crush or the movie you just saw, it's no big deal. But in polite and formal situations, proper spelling and grammar are still expected: It marks them with friends and strangers as intelligent people who care about the things they write.
Bottom line: If you want people to think you have a brain, write properly.