We communicate by speaking and writing. The rules governing speech are, as a rule, less strict. We use words to communicate and our brains are deft enough that most people automatically KNOW if the meaning is possessive or plural. The meaning is taken from context.

Grammar is in Dialog the verbal/written equivalent of Social Manners. It may be nice if people know which fork to use for what course in the meal, but eating your peas with your knife and with the edge of the tablecloth tucked into your collar to keep food out of your lap still gets the job done.

In my youth I learned this the hard way, accidentally offending a friend by pointing out the grammatical errors in a letter he wrote--he never wrote to me again. You only make that mistake once. I'm an English major, but my brain is always ahead of my fingers when I type, so there can be some bizarre typos and marks in my work. I try to proof it myself, so usually let it "cool" and come back later to fix the mistakes. Corrections may be absolutely necessary to be sure a legal document conveys exactly what it is supposed to, and poetically it's important that your work says what you really mean to say, but in most contexts, it's ridiculous to get bent out of shape about punctuation and grammar if that obsession with correctness allows you to miss the point of the communication.

That said, I have a Sharpie in my handbag and I have been known to edit signs when they are misspelled or poorly punctuated. Wendy's Hamburgers finally took down the little signs on their drive-through windows that read "We Don't Except Accept Checks." ;-D

SRS