My wife and I read a lot of books to our 2-year old daughter, as she brings us a constant supply of books asking us to, "reeeead." There is a growing stack of children's books in her room now that get my "stamp of stupidity," because of bad grammar, incorrect punctuation, slang speech and a general lack of discipline in something that is essentially teaching our kids how to read and speak.
I see it now a lot in the Chicago Tribune and other major newspapers that should employ more experienced copy editors—or even someone who has actually graduated college to do the job. Professional web blogs are littered with terrible English. Some of the industry books written by presentation specialists could use another once-over, as well.
The lack of proper grammar in the written word is bordering on epidemic. It's fine in a text or on Facebook (though it still makes you look stupid), but when you are presenting anything to an audience, it is always in your best interest to make sure your Ts are crossed and your Is are dotted. Literally, and not figuratively.
Internet conversational communication has made us all stupid. It made us lazy. We have forgotten how important the written word is, and how your use of the English language says a lot about you (and potentially your company).
It isn't that much to ask that when you are putting something together for a presentation or anything that puts you out in a spotlight, that you let someone else look over your words. At least proofread your own work. Worst case scenario, let the obligatory spell check have a glance at your efforts to make sure that you are on point, and not looking like a fool.