What is a fact? There are two kinds of facts: things and events. New York City is a factual thing. The city Is there for all to see, so we have a clear idea about the existence of New York.
Factual events are a little more complex, because we can see that there are two kinds of events, objective and subjective. A storm is an objective event, and a personal, individual experience is a subjective one, and of course is a little more difficult to have a clear idea of what is going on, particularly when the subjective event happens to others and not to us.
The alien abductions meme is based on subjective experiences, and it is logically impossible to know if we are dealing here with a factual event or something else like self-delusion or rationalization.
Looking for evidences we find that this idea, this subjective experience recognizes several hypotheses.
The most popular is that these abductions are committed by Aliens or Extraterrestrials.
The second one is that human agencies are responsible for the abductions.
The third one that we mentioned already is that abductions are lies, self-delusive, perhaps planted narratives or rationalizations of dreams and altered states of conscience.
From our own perspective, the Alien hypothesis demands some kind of evidences.
If millions or even billions of individuals are abducted by Aliens and submitted to genetic or biological experiments, the social and psychological impact should be detectable. Besides, there are no reliable physical evidences of the event.
The argument of aliens imposed amnesia and regression through hypnosis doesn't help to make the whole thing more believable. It is a fact that the hypnotizers that believe in the ET abductions directly or indirectly impose their own beliefs to the hypnotized. Besides, the so called regressive hypnosis is questionable and unreliable.
The second hypothesis of the abductions performed by human agencies is also not credible, first because the whole operation would be practically impossible and second because such maneuver would have no political, social or psychological meaning.
So must consider the ET abductions a meme, which is "an idea, behavior or style that spreads from person to person within a culture." Memes that are analog to virus, self-replicate, mutate and respond to selective pressures.
Memes live in the mind of the people and can be strong and massive, even if there are based on unclear ideas not supported by objective facts.
It is obvious that sharing an experience helps to find something in common with other individuals and communicate with them.