Interesting one this, currently on a well known Burnley fans forum there is the following debate:-
If a player commits a foul worthing of a booking, but the ref deems the situation to play advantage. The ball is in play for say a couple of minutes and at the end of that spell the same player commits another foul, is he booked once or booked twice and sent off?
Unlikely to happen of course! I guess the right decision is to send him off but is this hard to put in practise