I think users of reddit still approach it like it is composed of outsiders (even though it isn't). For example plenty of people I know use the site but people don't talk about it like they would twitter. Using twitter is a sort of normal social network. Reddit is treated far more analogously to a tv show that some people like and others don't.

Of course I can't really back this up with anything as it is just a feeling.

I didn't know it had grown that large. How much bigger has twitter gotten in the last two years?

I agree that in the context of journalism it's a loaded term that's probably not fair.

The outsider status is about more than the user count though. They maintain that status with all the weird stuff they get up to.

I don't think "cult" means "small group" in this context, but "strongly followed".

At least, that is how I always interpreted stuff like "apocalypse now is a cult movie".