For an IT shop, each worker's salary/wage sets their base pay and is confidential, while a biweekly or monthly "bonus" check could be the profit sharing reward. In that environment, everyone knows when business is going well and everyone knows when it isn't. Profit sharing can (and should) be open for discussion among all employees.
So, take Joel's example: Noah helps make an additional $1 million in a year for Fog Creek. What's that going to translate into for each employee's profit sharing check? I'll assume that Joel's generous, and that the ads are wonderfully profitable, so let's say an additional $400/mo/employee (average) while the ads are active. Holy shit, Noah, thanks! So, Noah get's more. Noah gets recognitions. Noah's coworkers get more. The company makes more. Hell, even Joel gets to make more. It's win/win/win/win.
And don't get me started on company stock. Stock is fine in many cases, but that's not what successful organizations make. They make money! Share it with the employees. They deserve it. 'Cause here's the thing: If your take-home wage isn't tied to your performance or the performance of the company as a whole, what exactly is everyone's motivation? Oh, sure, some people are going to do a great job no matter what, but that's not what really makes a company great, now is it?