I realize I'm jumping in late on this discussion, but it caught my interest.
Tball brought up Patrick Deneen's video about hands, and I have watched this video over and over again, mainly because what he is doing looks really good, and I would like to look like that. I have noticed that if you watch many of the current top bump skiers, especially on the US team, they have really quiet hands with an almost unnoticeable pole plant. This is a fairly recent change. If you look back at Jonny Moseley in 1998 and 2002, his pole plants were far more noticeable and there was far more hand movement. I suspect that quieter hands create the illusion of smoother skiing and better turns when being judged.
In my opinion, the pole plant is not a necessary movement, although it is extremely helpful to most skiers. Someone mentioned that your poles, via the pole plant, provide you with large amounts of information, like antennae. I agree with this idea, but I think they can be a bit of a crutch too. Instead of keeping our balance in check, we let it drift a little bit, knowing we can use our poles to bail us out a little bit. I'm not planning on throwing away my poles anytime soon, but I certainly recognize that when they are there, I rely on them, because its easier than really focusing on my balance and timing. If I ditch the poles for a run or two, I realize that I have to pay far more attention to everything else to make it all work.
Like Josh Matta said above, if you ditch the poles and focus on balance, the timing of the pole plant becomes irrelevant. Going back to my point about bump skiers, their pole plants are so slight that I doubt they are doing much of anything in terms of balance, and I think that is the point. The best bump skiers in the world should have exceptional balance, and as a result don't need to rely on their hands and poles to keep their balance.
Somewhat related; did any of you notice the pole plant technique used by the Soeurs Dufour Lapointe in the Women's Moguls at Sochi? It drove me nuts while I watched, but it seems to work for them. They reach forward with the tip of their pole well in advance of the plant. To me it seems quite similar to what was discussed here with regard to the four fingers and extending out the pinky and ring finger. I have since noticed it in my own mogul skiing, and it feels somewhat defensive in nature.