Thanks for the input guys, I think it's a valid concern. Nobody wants to pay for something and then have an arbitrary, anonymous Internet user yank it away from them. When faced with a situation like this, I always like to take the emotion out of it, and look at the situation 'by the numbers':
MilPoints Awarded: 168,820

(47%)
MilPoints Deducted: 190,560

(53%)
Difference: -21,740

So as you can see, there are more MilPoints deducted for 'bad' posts than awarded for good posts. I don't believe that's an accurate representation of overall the quality of our posts here... but then again, points are only awarded or deducted for "exceptional" posts, either good or bad. Some more numbers:
Total times MilPoints have been awarded: 1,291
Total times MilPoints have been deducted: 1,079
Average award: 131

Average deduction: 177

Total messages on Army.ca: 927,086
% of messages assessed: 0.26%
Interestingly, more people award points than deduct them, yet more points have been deducted overall. This is because the average deduction is larger than the average award. This implies several things. The amount you can award or deduct is based on your MilPoints balance. The higher your balance, the more you can giveth or taketh away. As the deductions are 26% higher than awards, we can assume that members with a higher MilPoints balance are more apt to fire a shot than give out praise.
Generally a user's MilPoints balance is a reflection of their time spent here, and the overall level of respect they have earned. In other words, it's somewhat a representation of your
seniority here. I'm going to go out on a limb here and say what everyone is thinking:
I have just scientifically proven that senior members of Army.ca are crusty. 
I'll end with just a few more stats:
Total MilPoints earned by all users, via all means: 7,005,166

Total MilPoint events: 419,478
% of events that are user assessments: 0.56%
% of MilPoints earned by assessment: 2.4%
% of MilPoints lost by assessment: 2.7%
This also means a few things... it means that while the assessment system can have a huge impact for a user, it's not tipping the balance of the system as a whole. However, since 0.56% of events can control over 5% of the balance, it also means that assessments probably carry too much punch. In fact, if you strictly believe the numbers, maybe assessments are 10 times too powerful. Maybe they should range from 5

to 30

instead of 25

to 300

.
So when all is said and done, I think the points made on both sides are valid: let's discuss some options that are fair but still encourage positive participation and "think, then post" behaviour on the site. I like the notion of "protected" points... it's going to take some effort to flesh that idea out and see if it's feasible... then to implement it if that makes sense, so please be patient and keep the ideas coming.
Thanks
Mike
Edited to fix a simple math error. 