For example, I saw a sign at my local grocery store: "Return your cart's here." After eight years as a college English teacher and even more years as a newspaper editor, I have been know to correct offending signs with my pen.
I once sent a letter from our college president back to him, corrected, with this note: "Need to develop the content, work on the grammar C-"
I agree.
One of the other mistakes I can't abide is the misuse of imply and infer. They are not the same and far too many people use them as if they are synonyms.