I don’t even know what "should of" means.
Yet I see it written in texts and emails all the time. Even worse, today I read it in a book. After the second occurrence, I had to put the book down. Arguably, that was just the literal spelling of the narrator’s pronunciation of "should’ve" in dialog, and I should have (hah! should have!) just let it go as an exercise in dialect. But I could not. Really, just could not. DNF.
It makes my eyes and my brain hurt to read "should of".