If I recall correctly, those who study such things have a formal definition of "cult". It doesn't just mean "new religion", or "weird religion", or "religion I don't like".
From memory, there are four parts of the definition. First is aberrant theology. That is a property of the belief system. Second is emphasis on "you must be part of our group". That's a property of the organization. Third is that they are heavy on control of their members. Again, that's a property of the organization. And I don't remember what the fourth thing was, just that there were four of them.
The number of points defining a cult change depending on who you ask, but from my experience they all have this in common - whatever the definition you take, Roman Catholic Church is definitely a cult under them. Some companies too, likely. Or pretty much any organization formed by people who decided to approach some issue seriously. Hell, haven't you heard that Hacker News itself is a cult, and pg is its leader? Or Less Wrong and Eliezer.
Of course, it is useful to have a concept to describe organizations centered around some bullshit beliefs, that lure people in and then harm them, but it is very hard to make a definition (especially for the "bullshit beliefs" part), partially because a lot of features assigned to cults are in fact features of efficient organizations. You have to evaluate beliefs and intent on a case-by-case basis.
It takes a lot more than bullshit beliefs. In fact it's not about beliefs at all, so much as exploitative, manipulative, controlling behaviours.
IMO HN really doesn't qualify. Nor does Less Wrong. YC may have culty tendencies, but it's still quite a way short.
Some businesses and startups are close to the edge, and a few are probably on the wrong side of it.
Scientology certainly qualifies. (I suspect people who haven't looked into it have little idea just how incredibly weird Scientology is as an org, never mind as a belief system.)
So do some churches.
The hard part isn't finding cults, it's working out how damaging the experience is. I know a couple of people who spent a lot of time volunteering for a cult in California. The leader was a genuinely dangerous psychopath and exploiter, but they don't seem to mind because they never met him personally, most of the people they met were nice, and it's where they met each other.
That may be unusual, but cults often collect curious, generous, and rather insecure people who are herded and abused by a few crazies. So it may not be that unusual to have a good experience, as long as you can avoid becoming a toy/servant/sex slave/cash cow for the leadership.
Creating all of the above is the true aim of every cult. The bullshit beliefs are just the window dressing.
From memory, there are four parts of the definition. First is aberrant theology. That is a property of the belief system. Second is emphasis on "you must be part of our group". That's a property of the organization. Third is that they are heavy on control of their members. Again, that's a property of the organization. And I don't remember what the fourth thing was, just that there were four of them.