[wisty]

http://www.ericsink.com/bos/Closing_the_Gap_Part_1.html

In sales is relatively easy to measure performance. A sales guy's commisions should be a factor of the value they add to the company based on how much they sold.

Obviously, they'll be slightly loose cannons (lying to get sales), but that's part of the cost of having them.

You could just hire sales guys and not pay them a commission, but ... their intrinsic motivation will be close to zero (would you want to do their job?) and it's too hard to manage them without incentives.