Imagine it like this..
Someone new comes on, makes a minor mistake because they are fairly new to minecraft and this community.. They offend or annoy someone charismatic or they bug the community as a whole over something minor and easily forgivable..
A dozen users suddenly give them negative reputation.
Before you know it, someone's rep is trashed because on popular person didn't like them, or a group of people found them kinda annoying.
One day, you just don't wanna hear someone ask questions about basic stuff like how to get out of spawn or do craft something.. Blam, their rep is in the trash for months, if not the rest of their lifespan on SC, because they just found the community on a bad day.
A snowball rolled down the hill starts to become a boulder.. One person triggers it, everyone falls on a single person like a frenzy.
Look at it from the other side. One person is having a personal spat with another. The reputation system gives them a chance to vent that spat and have their friends and allies help vent that spat by making that person seem horrible. Your reputation is ruined because you had a minor disagreement with someone. New players assume that you do horrible things, and don't trust you.
Yeah, it's just not a good idea, because of the chance for abuse. Even allowing Admins to use it exclusively, what if they just got pissed off that day, acted on those emotions, and before there is a chance to take it back, someone is labeled a bad person.
We are only humans, and humans can be petty and bitter, without even intending it, and with no true depth of malice behind it.
Not everyone will get along, and when we don't, we will strike at one another eventually through whatever means we have available.
