I agree that "infected beers" can be downright nasty, but they won't kill ya.
I was thinking more along the lines of someone doing something malicious or really stupid (e.g., "Hey, I bet I could make a gruit out of {XXXXXXXX} flowers, leaves, and/or wood/bark"). Even appropriate substances, when taken to extremes have given me pause as to the maturity and intent of the individual entering the beer/mead. I've tasted a jalepeno pilsner--delicious and refreshing; and the pepper wasn't too overpowering. But, I've also judged a mead made with chipolte and serrano peppers that was a weapon of mass destruction (liquid fire) and basically devitalized my tastebuds for the rest of the day. A sip was all it took. One could not drink an ounce or two, let alone a whole bottle of it. Afterwards the excuse was that the entrant had not sampled the mead prior to submitting it for competition but thought my comments on the judging form were hilarious. ???Really??? Had I travelled out of town and paid for a hotel room to judge this mead in the competition, at a minimum, I think I would have sent this clown a bill for wasting my time and getting cheap sociopathic thrills off of hurting random individuals who had the misfortune of having to judge his entry.