> Still, the level of ostracism in mainstream religions is nothing compared to, for example, what happens if you try to leave Scientology.

Worldwide, a majority of muslims support the idea of a death penalty for apostasy (renouncing the religion).

Defining a cult is a lot harder than it sounds at first glance. My personal definition, which is not very useful since it's so subjective, is "A cult is a new religion formed on purpose by a charismatic person who is knowingly lying in order to gain temporal power."