Heh. Seems that some things never change. I took a hiatus when all this started and it seems it continues to pop up every so often. Now...
I haven't played with you new guys (or with the old group) for quite a while, but it seems to me that the original issue was with people leaving when they really don't see any point to continue. To take up the original example, remember that, if you don't have any more Smelters and little resources, building a new one won't help.
At all. Especially if you can't repel your opponent's attack. Of course, if you choose to use those resources to build the units you need to attack, then you have another problem: Your resources WILL eventually run out.
In other words, it's a lose-lose situation with negligible chances of winning (unless you get lucky. How? Dunno). I admit that I've left games, but I have always done so under one of two conditions:
1) Zero chance of winning: You understand what this means, right? If you don't, look up the words. It means that you can't win, save a miracle help you. Those people that allow your opponents to rebuild, you're nice and all, but... we feel threatened every second of the way. I'll be the first to tell you that it's not pleasant.
2) Other commitments. Easy thing to understand: REAL LIFE > GAMES. We live in the real world, not in the game world. We don't all have the time to spend playing. I make it a habit to tell my opponents that "My life intrudes upon my game time once more" before leaving. Needless to say, IT HAPPENS!
Of course, there are people that leave for no reason! Those are the ones that spite you. Mean as they are, they're human, and that is their temptation. You have no other choice but to LIVE WITH IT, since it would be plain insane to threaten them in real life.
At any rate, those are my two cents.
Oh, and... Hey, y'all. Hope you've been well. I'll be trying to get into IRC soon.