I can see one of two things happening. there are any number of things, anticipated and unanticipated, that could come from this. I'm excited to see what those things are. Kick the tires, have an open mind about it and please keep sharing your feedback. It's imperative.
Vindictive users could abuse this, bots could abuse this, etc.
Keep in mind that you yourself only just got the ability to add a community tag. Bots will not have an easy time gaining this ability. Vindictive users are usually vindictive in all aspects of their use and easily identified and filtered.