I think it is important to have a mix of variable compensation - it's good to get to a discrete level, but there needs to be an incentive to reward team behaviors. Years ago when I worked my way trough college waiting tables I was struck by how much better the level of service was when the wait staff split tips vs. fending for themselves. Same thing holds in pre-sales. Too much individual reward and reward on individual deals means that people act in their own best interest and not in the team's interest. That leads to some individuals over-extending themselves in seeking to be part of more deals to gain more money. All that usually leads to is a worn out pre-sales rep, doing a poor job in many accounts and the company not winning as much as it should.
--Steve

That's a great point. As usual there is a delicate balance to strike here. I still believe that at least paying pre-sales at a district/geo level (say based upon 6-10 reps) as opposed to the entire US or Europe is a better proposition. A little more risk, but way more upside.
--John/MTS