I don't concede games often, but the situation that really cracks me up is when my opponent concedes all games (many times because of lack of patience and other personal issues mind you), and then I'm EXPECTED to concede his 9 balls. That just makes me laugh every time. People really need to get a clue and think about stuff.
Edit: also, many people think conceding a game is a "favor" every time. We'll I'll tell you, dont do me any favors especially when you're conceding every one and then it's like 7-7 in a race to nine and you approach the table and then step back on my 9ball shot. This the the "im a good guy who concedes...... but really im a cheating a--hole" routine. This is probably far more common than true altruistic motives, which are rare to nonexistent im sure. THE POINT I'D REALLY LIKE TO DRIVE HOME THOUGH IS THAT MANY TIMES PEOPLE CONCEDE GAMES BECAUSE THEY ARE RAMPANTLY IMPATIENT AND CAN'T STAND TO LOSE AND WATCH THEIR OPPONENT POCKET EVERY BALL, they just can't hack it, so they wait until the last possible moment that they figure the guy can't possibly mess this up..... gee, some "favor", thanks a lot. Get some self control and certainly don't complain when I patiently sit in my chair as you shoot your nine balls. It is really laughable if you can truly read what's happening.
Mind you, i have NOTHING against conceding games, just people that expect it to be reciprocated due to their own inadequacies (which isn't always the case for their conceding of course).
ps, the poll should have more options
such as "i concede games at times to gentlemen i respect but usually not to crack heads that run around the table and can't sit still"