I think you'd have to be pretty ballsy to only apply to one school! I applied to 4 last year and only got waitlisted at one! (rejected at the others) But this year I've been accepted at one school and am interviewing at my #1 choice... after applying to seven schools.. Obviously it helps to have a safety net
I only applied to the University of Oklahoma as well and got in Dec. 1st.
I mentioned that fact in my personal statement and my interviewers also asked me if I had applied anywhere else.