This is an odd one, but here we go:
About 6 weeks ago I brewed a Schwarzbier, and aerated it using my usual method: a 2" long chunk of 3/8" vinyl hose with a hole poked in it -- my ghetto venturi aerator.
Somewhere during the transfer, disaster struck, and the vinyl hose ended up in the carboy (and a gallon of schwarzbier ended up on the lawn) but I pulled together, finished 'er up and recovered. By the time I noticed the vinyl hose had disappeared into the carboy, I figured "how much harm could it do, anyways?" and wrote off any efforts to retrieve it as too damaging to the beer overall.
Tonight I finally racked it to secondary, and when I recovered the vinyl hose, it was still in one piece, but was discoloured a vibrant yellow, and smells strongly of urine (ammonia?) when you hold it to your nose. The beer itself doesn't seem off in any noticeable way.
So, folks, is this actually a concern, or was my original hypothesis ("Totally not worth worrying about") correct?