Well, shit. What do you imagine the guy to my left has? I'll make it easy for you. He's going for a flush in the sou suit, or perhaps a chanta (all outside tiles [123, 789] and honors). His discards make chanta unlikely. Meanwhile I have four pairs in the hand, and I've been thinking about seven pairs. Right now I'm thinking "but how am I going to assemble that without letting go of these sou tiles?"
Well, then. The answer is going to be that I don't go for seven pairs at all, and instead attempt a normal shape. Discarding South I can pon 4m, 8p, or 8s and be in tenpai. If the player to my left lets go of 6p or 9p, which is likely, I can call chi and be tenpai that way. These are cheap options, but it'll stop this guy and that's what I'm going for. There is the chance that he's waiting on South as part of his flush, but I go on ahead.
Tenpai. I can discard 7p (the dora) for a double pon wait on 4m/8p or I can discard 8p for a double-sided 6p/9p wait. Generally, when you're presented with this choice you go with the double-ended wait: you're waiting on more tiles that way. And in this case the double pon wait involves throwing out the dora, so screw that. I go with the latter. Hatsu, dora 2 is a pretty solid hand: mangan if I draw it, 6400 if I don't.
I do not reach. I am leading by a small margin, just 2700 points, and the other players are probably more worried about holding on to sou tiles. This is the perfect time to sit back and let them deal into me. If the player to my right deals in, he's busted and it's over. Worse comes to worse, I can still fold.
Oh ho ho, what's this? The player to my right is in dire straits. At 1500 points, he needs a huge direct hit to make it out of last place... and he's let go of a dora. His hand is at least close to complete if he's willing to let go of that in his desperate situation. So I change my mind and reach on the next discard. I think all three of them are liable to deal into me now.
Though he isn't close to tenpai after all, he is desperate, and, yes, holding on to those sou tiles. I get my tile on on the very next discard. With reach, ippatsu (one-shot) and an ura dora my hand goes to haneman, 12,000 points. Player to the right is very busted, and this game is over.
(A little hindsight from the replay: the player to my left actually wasn't tenpai until long after I was. The calls had been a little hasty.)