I know that Language Log has already (e.g. here) mentioned the widespread would of, though I haven’t seen a whole lot about the gradual expansion of that of into uses like hadn’t of where there never would have been a have (oh! I tried to be funny and write ‘would of been’ but Word automatically turned it into 'would have been' – but at least its little pop-up offered the option of restoring it and even to “stop automatically correcting ‘would of been’” – that’s very open-minded of them!), suggesting that 'of' is becoming a general marker for counterfactual modality, but I just have to report a really beautiful example I heard on my favorite public radio station, WFCR of Amherst, on Feb. 16 during their recent fund drive, out of the mouth of a very literate member of their development staff, K***, –- I’ve even met her and been interviewed by her, and I won’t name her simply because she might be embarrassed and I wouldn’t want to cause that. You know how the announcers have to just keep talking all the time to try to fill the time interestingly enough in between repeating the phone number to call – I’m impressed that they stay as coherent as they do. Anyway, the other announcer, a regular classical music host, had just said something interesting about some composer, and K*** replied, “I didn’t know that, and certainly wouldn’t of have without listening to WFCR.”