The problem here is that I can just see the average American drinking several bottles of it a day because "it's good for you" and especially because "it tastes good".
I actually just last night had an upset stomach from this ham I ate, and got to the point I couldn't even drink water as my stomach would send it right back through my mouth. I'm at this very moment sipping Kambucha and am feeling better already, plus it's not getting rejected. Of course I won't have a whole bottle. I know for a fact that in Russia they drink a small shot of it daily and not giant bottles like they sell them here clearly with the commercial intention of having folks drink them by the dozens.
Risks exist in everything you do in life including taking prescription medicatuib. Just read the side effects of any in your cabinet. It will be a lot more extensive and serious than kambucha's.
Moderation and common sense is the key.