I've been here long enough to remember the old days. When someone with real knowledge gave notice, management would scramble, make a counteroffer, promise to make necessary changes. They'd do whatever it took to keep them.
That doesn't happen anymore. I can't recall the last time someone stayed because they got a better deal from us. People give notice and management just says okay, good luck. That's not smart at all, in my opinion. It'll cost us in the end.