>If they succeed, then you will almost certainly be unable or unwilling to pay them what some other similar company would pay them now that they have proven their ability as a lead. They will stick around for a while, but once something starts to go wrong anywhere on their team or in the company (and it will) they'll realize that it's probably going to be several years before there's any potential to climb the ladder any further, and they start to sniff around for what they should be making, and you'll lose them.

Oh wow. This was the EXACT thing to happen to me.