I still feel bad for kuke that they banned cacti. I vaguely remember when you could place Cactus.Long ago at the spawn there was a cactus with a sign next to it saying "Offer your diamonds to the cactus god! Good times.
So to be honest I had no idea how a dropper worked until about 5 minutes before writing this. This is a quote from http://minecraft.gamepedia.com/Dropper So in this it tells us a bit about the functions, like the 'upwards elevator' for items and 'pulling items from containers'. This sounds a lot like some kind of way to make an automatic form of making money. Not sure how it would be done, as I've never used them, but there may be some possibility. They also might just be banned simply because they can cause lag. To be honest I'm not sure why they are disabled, but I hope this helped you out. If you have anymore questions, let me know Inamine *Edit* After scrolling through some entries on this thread I believe that droppers were disabled due to a duplication issue we had.
Unknown took away like half a stack of stacked tool from me, he said I'm nt allowed to have them so ad that to the list.