Battered by waves of downsizing since the 1980s, talented men and women no longer seek job security from one company. This is the true hallmark of the new economy--not fleeting dot-coms and IPOs, but a fast-moving, free-agent workforce with the flexibility to jolt productivity. Managers, meanwhile, must grab hold of this shifting group of talent and squeeze more work out of them than ever before, particularly in a tight economy. The trouble is,...