I worry about this often, since pretty much any quick release anything is removed from bikes in rather short order on campus. Seats, wheels, etc. Often times, you'll see the discarded frames of bikes that have been stripped down - though the one I'm thinking of sat there for more than a semester. But, wheels and seats are hot targets and for that reason I run my cable lock through the seat rails and the front wheel as well as the frame. That whole mess gets locked to the bike rack when I get to work or class.