I've seen a lot of people write "could of" for "could have" recently. It seems like they heard "could've," assumed it was "could of" and started spelling it that way. Is this common? It bugs the heck out of me...
Oh yeah ... all the time. I think it's largely due to people basing their spelling on what they hear, and not doing enough reading. When a language is "learned" primarily by the ear and not the eye, mistakes like this are common.
I recall a student who wrote "for all intensive purposes" and meant "for all intents and purposes," because that's the way it sounded to him.
As a personal example, while a student myself, I thought for some time that the Taj Mahal was the "Tajma (or however I spelled it) Hall." Didn't dawn on me I had it wrong until I finally saw it in print.
I have seen all three as ... of. I've also seen I'd of. It bugs me too.
I teach at a university, so I read students' papers on a regular basis. *Could of* does find a way to sneak in and punch my eyeballs 🙂
It never occurred to me before, but I guess if "all intensive purposes" is the same sort of thing, then "could of" and "I'd of" must be mondegreens, even though they're not in song.
One that seems to attract especially emphatic winces from me is "try a different tact".