Yeah, I read into that stuff largely out of a curiosity about memetics too :-)

It's the thing someone is worried about when they say "Has Bob joined some sort of cult?"

I like "the mom test" for that. If you're hanging out with a group based around a common set of beliefs that are taken by the group to be formally true, would you be too embarrassed to ask your mom for advice about the group or the beliefs? If so, then for you (given your parents and their community and so on) it's close enough to a cult that you really should stay away (unless you're just doing participant observation as a research project). On the other hand, if you're not too embarrassed, then you really should actually go ask her for advice, because that kind of practical and emotionally grounded feedback is good input for people to be mindful of, even if it isn't always perfect.

This is a primary reason I recommend that people talk to one or both parents about SIAI if they start suspecting that they should get personally involved with existential risk activism and FAI and so on :-)