I know how we have the @ tagging feature, so why not go all the way and add a # hashtagging feature? With it could come a whole tab with users who tag what, how many tags, etc. Then, in each post, there could be a fancy tag image at the bottom with the tags. Finally, you could set a maximum amount of tags per post and an error pops up if they are exceeded.
Possible feedback, ideas, +1's always welcome