I play a lot of pvp, most of it on WoW, some of it in FPS format. The concept of "balancing," and its attendant justification of "nerfing" has seen a lot of discussion now that arenas are out in WW. Balance is bunk. The reason designers don't achieve it is because they don't want it.
Don't worry -- despite the teaser this isn't a rant brought on by losing to a better player. That happens to me too often to warrant complaint. I want to argue that the basic goal of "balancing" -- even the standard model of "rock-paper-scissors" balancing (rogue beats warlock beats warrior beats rogue) is misleading, and does not explain what we see in game design.
These thoughts were provoked by my experiences in the World of Warcraft Arena. I play there a lot, and really love it. I have been struck by how smart people are. For those of you who don't play WoW, I'll just claim that there are quite difficult to find solutions to combat problems, and players move to those solutions with frightening rapidity. Corner solutions -- solutions built out of finding one extreme behavior and repeating it (paladin / warrior groups for examples) are the norm. Other corner solutions I've seen -- all stealth groups, where the priests are nightelves and can shadowmeld. Or, in 2v2 combat, two warlocks who have the same specific rare item that raises pet abilities beyond the ken. Suddenly the pets are a serious problem where they were a nuisance before.
Ok. So. We have thought of balance in pvp as a progressive task. The standard model of balancing says that we get "better" balance by introducing new powers, or nerfing old powers. The goal is an equilibrium, whereby everyone has fun and has something of a fair shot in pvp. Even the "rock-papers-scissors" paradigm seeks a stable equilibrium. Mages can kill warriors, can kill rogues, can kill mages, and so on.
My sense is that this is simply not what is happening. Rather, nerfing, buffing, and more is a solution that seeks to DISRUPT equilibria. Any pvp system will fall into stable states, mostly as a function of people's ability to pick groupmates and select targets. Buffing and nerfing disrupts that equilibrium and sends people back into experimentation mode, as they seek new corner solutions.
Thus, people who complain about nerfing do so because it disrupts equilibrium. And people will complain about any nerfing -- or any buffing (because the upcoming buff to warriors is a nerf to little ol' rogue me, believe you me) -- not because they are concerned about progressing toward "balance," but because any change disrupts the current equilibrium.