I've touched on it on HN before but I also had a very, very bad trip once. It wasn't the first bad trip but it was the worst and one of the worst I've heard from people who I've shared the experience with. Out of the dozens or more positive experiences I had, it was enough to turn me off of psychedelics and drugs in general for, so far, the rest of my life.

I won't get in to the details, but like yourself, it mostly came down to the folks who I was with (who I trusted absolutely prior to this experience). I also had a lot of the blame, because I simply took too much that night. It took me years to fully recover my personality. To me, it is very dangerous, indeed, to suggest that nothing bad can come from psychedelic experimentation.