I am a proofreader. I have many grammar/usage pet peeves. Jan, you must have heard of the book Eats, Shoots and Leaves?
When I'm writing/reading online, I try to understand that my, umm, formal language isn't the norm. Texting is hard, though, because people want to be fast: texters not only want to respond using as little time as possible, but they also want short responses (i.e., quickly read responses). I guess I'm saying that I try to think of my audience.
But no matter the medium, if I'm not getting paid, then I try not to go too nuts.

There are exceptions. The film title "Two Weeks Notice" still bugs me It should be "Two Weeks' Notice." How was that missed by the 1000s of people involved in making the film?! Not a single person working at the studio knew what "genitive" or "inanimate possessive" means?