I always have a couple of cold ones during the boil and so far everything has come out fine. Several years ago we had a hatch of periodical cicadas with some of them flying around while I was brewing outside and I wondered how many of those were going to end up in the brewpot. As far as I know, none of them did, but along with a suggestion from one of the contributors to this forum I called the batch 8th Plague Ale. It was good!