"...I have no clue what the motivation is for these moves, nor do I knows what what they were in 2006. But they are looking increasingly curious and ill timed. Once is a coincidence. Twice makes you pay close attention. After the third such move, expect to see the index managers dragged before a Congressional panel..."
Being aware of these kinds of events in advance is the kind of ninja move that really makes the difference-- I sold at 860, and will re-buy at around 810. This means I get more ounces for the same money. However, I hadn't really considered that this isn't something that's done on a consistent schedule. Why not do it annually, or quarterly? Rebalancing inconsistently seems sketchy.
Interesting stuff-- thanks to reader "Alfred" for the link.