I read an article recently on CNN.com about how many feel that text speak is too casual for romance and how it doesn't promote clear communication. In one example, a female received a "U out?" text from a guy she'd gone out with several times.

Out of the relationship?
Out of toilet paper?
Out of the house?

My team reviews all software screens, instructions, and error messages. Lately, I've seen a lot of casual language from the text/Twitter generation.

Know your audience. If you work for a cutting-edge marketing or advertising firm, then this doesn't apply. Know that the rules are different depending on what you're doing.

If your environment is traditional, instructions, user guides, and reports need to be clear and in standard English. If you use acronyms, make sure that you define them. Make sure that readers can pick up on the context clues.

You're not doing your job if the readers can't find the intended meaning.

(This applies to your resume too. If you're polishing up yours, get rid of the slangy stuff.)