Before we ended our one-week classroom session in WRT 307, we talked a little bit about the use of informal writing in technical and professional contexts.
I just read a brief note about a Pew study which shows 64 percent of teenagers admit they use informal writing styles in their school work. There is the now folklore story about the British student who submitted an assignment written entirely in text message shorthand. That's not what the Pew study revealed. More specifically (and perhaps more challenging for writing instructors), the study indicated that young students find it acceptable and easy to integrate emoticons, informal punctuation and grammar, and text message shorthand while authoring in formal contexts.
So rather than take a hard-ass instructional stance, it seems that our challenge as teachers of writing is to understand how these stylistic changes affect what we're trying to achieve in the classroom. And perhaps the challenge is greater for professional and technical genres: integrating informal styles in such a way as to not compromise the organization, logic, structure, and concision of a document.