Or "Who do you hang with"--"who" is the subject form, and "whom" is the object form; "who" is the subject of the quoted sentence as posted.

It's sad and ironic; using "who" in object position is a common mistake, and prescriptivists (grammar nazis) often correct it to "whom". But in this case, "who" would be right, but the poster has seen the correction so often that they've applied that "correction" even where it's wrong.

PS - thanks for posting first and giving me an excuse to talk about it :)