I probably have flown the late flight into SNA 15 times and have had it happen 3 times, which is 20%. The other posters said it was rare, but it happened to them 5% of the time, which to me is more than rare. Obviously, the only flight this is really an issue on is the ones that get in late at night. I actually started flying out of LAX when it was going to be a late flight because of this.
It makes for a long night, but the airline will get you back to SNA if you want them to, or you can get your own transportation. They have a bus sitting outside baggage claim waiting. You will notice they are running close to curfew when the flight attendants start rushing everyone to their seat as you are boarding. I did get lucky one time when the weather was bad in Atlanta and the got a waiver to be 15 minutes late.