About half the people at Valve have run their own companies, so they always have the option not just to take a job at another game company, but to go start their own company. The question you always have to answer is, 'How are we making these people more valuable than they would be elsewhere?'
Gabe NewellEverybody understands that you're supposed to say 'our employees are our most valuable asset' to the point where, even if it's really true, they're not going to really trust you until you've earned that - same with customers.
Gabe Newell