You confuse StackOverflow (the company with 3 employees and Joel as a founding partner) and StackExchange (a product of Fog Creek based on the SO code). StackEx

You confuse StackOverflow (the company with 3 employees and Joel as a founding partner) and StackExchange (a product of Fog Creek based on the SO code). StackExchange's revenue is less important than the revenue from StackOverflow which is currently derived from ads and the careers site.