I'll believe it because I had to be "that person who drives people home after a rave" a few times in my life. There's "I forget my name" drunk, but that's a joke, then there's people who are having a semi-bad trip who literally forget who their friends are. It never got as bad as this fortunately.
Use dissociatives responsibly, be in a familiar environment etc.
I do not agree that having a semi-bad trip makes you forget who your friends are. In fact, I wouldn't call that a semi-bad trip, at all. If someone forgets their friends while tripping (and I assume you mean on acid) they actually, likely, never liked that person enough anyway. Breaking down the barriers and lies is what it does.
I would assume as the poster is talking about raves, they are referencing ketamine or MDMA, and both of these are more than capable of making you forget who you are, let alone who your friends are.
MDMA absolutely is.
I am well aware that it is not ordinarily associated with hallucinations or disassociation.
I can also absolutely say that you do not need a serotonin-syndrome inducing dose to forget who your friends are, who you are, or have no idea why you have are sitting on a bed (your own), or who it belongs to.
It can also make you hallucinate and "disappear" into your hallucination for several hours, before you pop back into reality.
Finally, and not really disassociation and more hallucination, it can make the faces of your friends morph into other peoples and even appear featureless.
I'm sorry but that is complete bullshit.
Granted each drug has a subjective and unique experience due to the nature of your biochemistry, but by and large the experience of MDMA is relatively harmless. [0]
The serotonergic effects are a completely different matter.
Someone has misinformed you. Please do your own research. There is absolutely no mention of anything remotely like what you are describing in the wikipedia article: http://en.wikipedia.org/wiki/MDMA
when MDMA comes in pill form, it's usually called a roll and contains a number of things in addition to MDMA. Usually some other amphetamines like MDA, and a number of other possibilities.
Use dissociatives responsibly, be in a familiar environment etc.