Yes. JetBlue does not overbook. IDB'd passengers are compensated $1300, so I'd say that it happens once every few blue moons.

As with all other airlines, this does not include standby passengers. Standby passengers do not count as booked on the flight until they are assigned a seat. If there's no room, then they are not booked. Ticketed passengers without seats are processed and assigned seats at the gate before standby passengers.