I wouldn't advise doing it, to be honest! I accepted tea off all sorts of dodgy characters at free parties when I was a youn'un and I didn't give it a thought that they might have been poisoning me, or that there might have been a kilo of mushrooms in that brew etc etc I think my careless attitude ensured that I had good trips but looking back it frightens me a little.
If curiosity does get the better of you, make sure you do it with someone who knows what they are doing and you are in an environment that you are very comfortable in. These are the differences that could make the best and worst night of your life.
Some people experience some very nasty, realistic hallucinations, not to mention the paranoia as you come down. I personally have had no bad experience but I would be a fool to recommend it.