Not looking for house points here Tightslot, but I also believe in basic courtesies. I always say "thank you" (and something like "well done" if the crew were pushed for time) as I leave the a/c. It costs nothing and I like to think that it contributes to making your day a pleasant one. Too many pax now are too busy switching their damn mobiles on as they leave the a/c!
On the other side of the coin though, I have noticed a growing tendency for the CC at the back (of short European flights) to stay chatting in the back and completely disregard disembarking pax. So, when I'm close to the rear I often make a point of going back to say my "thank you".