Traditionally most people segued from undergrad to med school but nowadays I think many if not most people take a few years off (masters degrees, enter the work force, research, start a family or all combined! 🙂 ). Average ages at med schools have gone up.
There are many people who are successful reapplicants. I believe you can take the MCAT 3x and if you have to take it more you need special permission, so that probably has an effect on reapplication. However I remember reading an awesome story of one SDNer last year who got in after her 4th or 5th try.
Of course everytime you reapply you must strengthen your app.