Maybe I'm just feeling unfairly treated at the moment, but....
How come developers don't get commission for work done, and salesmen do? - the salesman sells the product which the developer then has to produce - (because usually in true salesman style - they'll answer yes to any question the client asks, and then leave it up to the developers to sort it out)... and at the end of it the salesman walks away with a nice bonus for doing their job, which is to sell things, and the developer gets nothing, for doing their job.
Hardly seems fair if you ask me.
Anyway - end of rant