"based off of"
What's interesting to me about this term is that it really does seem to be fairly recent--about as old as the now-no-longer-odd phenomenon of folks on the street talking on cellphones outnumbering those of us who prefer to simply walk on the street, saving our phonetalking for when we are in the home or office.
I taught my first undergraduate course in 1999. It's only in the last couple of years that I've begun to notice that nearly EVERY undergrad paper I look at contains this gaffe. And I'm not a prescriptivist, per se, but this just seems odd to me. How did it happen? How did it become nearly standard usage (at least among undergrad college students) in such a short time?