it seems to me that the times when people have bad trips on any substance, it is due to one of several reasons:

1) they simply overdid it and took too much of the substance
2) they were in the wrong environment with the wrong people
3) they have long standing psychological/psychic issues and/or are on medication to deal with the aforementioned issues…wellbutrin and psylocibin don’t seem to mix
4) they did no research on the substance and didn’t know what they were getting themselves into, thus becoming terrified when their world starts to unfold
5) they watched something disturbing on the boob tube, listened to violent music, or invoked dark entities

i strongly believe that with the right coaching, the right environment, and the right people, almost anyone can benefit greatly from a psychedelic experience…the right enivronment usually means one that the person is used to, one that the person trusts…or somewhere beautiful, like nature, away from cars, buildings and radiowaves…having someone like a “sitter” is often a wonderful idea, so the person having the experience can feel safe

any time anyone takes any substance (this includes cigarettes, alcohol, salvia, acid, etc.) i really think they should do some research into it before attempting to ingest it themselves…some great books on this subject are:

1) Food of the Gods: The Search for the Original Tree of Knowledge A Radical History of Plants, Drugs, and Human Evolution by Terence Mckenna
2) True Hallucinations by Terence McKenna
2) DMT: the Spirit Molecule by Rick Strassman
3) Breaking Open the Head: A Psychedelic Journey into the Heart of Contemporary Shamanism * by Daniel Pinchbeck
4) *The Doors of Perception by Aldous Huxley
5) Plants of the Gods by Richard Evans Schultes, Albert Hofmann, Christian Rätsch
6) Zig Zag Zen: Buddhism and Psychedelics by Stephen Batchelor (Foreword), Allan Hunt Badiner (Editor), Alex Grey (Editor)

just to name a few

always always be safe, always do what thou wilt in love and peace, always shine :)