By way of contrast, an engineering firm I am familiar with had an employee who had been there six years, and knew the company's very complex product inside and out, every nook and cranny. He was one of the only people who had such deep understanding of the system that he could fix any issues that might come up, hardware, firmware, software, everything. He gave his two weeks' notice, and then went to a different job. He's a very talented guy, who would command a very attractive offer, but his talent to the current company is vastly greater than his generic value on the market, because of his detailed knowledge of the product. Although he diligently documented his knowledge, the company was still left in a jam after his departure. It would have been great if the company had fought for him the way the law firm fought for the other individual described above.