I'm very curious as to what sold well and what didn't at the release of Cataclysm, when everyone was busy leveling up their characters (and creating new ones). I came up with several ideas on my blog over at WowSource.US (which is no more, maybe one day I'll be inspired to start back up).
One such idea was that everyone will be in to buying a ton of raw materials, and the counter idea was that everyone would flood the AH with them. Another idea was that 16/18 slot bags (crafted) would sell for ungodly amounts, but then championing for major cities allowed for cheap 16 slot bags.
Did you invest in any items before Cataclysm's release in the hopes of becomining the next WoW gold-capper? If so, what did you invest in? How did it work out for you?
NOTE: This is a very general question that does not request a specific answer, but rather a broad overview of the changes in WoW economics as impacted by the expansion.