It should be noted there can always be ways to game the system. The question is would reporting abuse, spam, and plagiarism be able to head that off. Also there are ways to game the system now with the down vote existing as long as those gaming it already have sufficient power and reputation. Anytime, we suggest something should be fixed we should consider the ramifications. What would it take to implement the change? Can we think of ways the proposed change can be gamed or result in even worse problems? What are the down sides.

The only down side that is legit is that every up vote taps into the reward pool. When you down vote something you return some of those funds to the pool to be distributed to the other up voted posts. This is not completely accurate, but it is more or less the idea. It is like that person at the store taking my money I was going to buy something I wanted with, going somewhere making change and then walking around the store giving a portion of it to all of the people who were willing to purchase approved items.