hbarsquared
Quantum Chronomancer
My own resolution for the "system breakers" syndrome is encompassed in a single word: No.
When someone wants spell interpretations that unbalance things, I say no.
Someone wants to pull something out of Psionics or Exalted Deeds that makes them overpowered, I just say no.
They want to make an optimized weapon for their five-prestige-class Mahem Master, I say no. (In fact, I probably said "no" long before they took their fifth prestige class).
When used fairly and consistently, this wondrous word keeps game systems playable for a very long time. Use it early and often!
Although I would agree in situations where the player asks for an unbalancing artifact, or free reign to stack damage after damage because of unnamed modifiers, this is not always the case.
So much of "unbalancing" is a surprise, a stumbling-upon of rules interactions, or a surprising synergy, or a trick, or whatever. It's hard to say "no" if it sounds fair at the time. It's even harder to say "no" after the fact.
I can see how the buildup can lead to, if not a need than a desire for, a new edition.