There was a brief period of time, reflected in some spells mined from the data files, when the Crop was going to be an item that would be right-clicked to enchant your mount with extra speed. This led to many people complaining that they would now have to buy one Crop per mount. Anyway, now that mounts are going to be learned instead of kept in the inventory, this doesn't work anymore, apparently. So Blizz is still undecided on what precisely to do with it. It does seem certain that it won't stick around in its current trinket form, and virtually certain that it won't disappear entirely, but everything else is up in the air. What do you think they should do?
Riding Crop. If you're level 70 (and not a druid) you probably have one, and if not, why not? Jeez, just buy it from your friendly neighborhood leatherworker already; they have few enough ways to make money without you cheaping out. However, everyone's favorite mount-speed-increasing item is going to be changing a little bit in LK. Blizzard realized that it's "no fun" to be swapping your trinket around all the time, even with addons, and that it's relatively common to be stuck in combat with the Crop equipped when you really want to have your Bladefist's Breadth or whatever. So they wanted to get the Crop out of your trinket slots.