The 'cult' word is inflammatory. To some, Mormonism is a blatant cult; to others its just a different version of Christanity. Waco, Heaven's Gate, Jim Jones come to mind, too...weird extreme fanacticsm, mass suicides.
We'd like to be clear how we use 'cult' and 'cultic' on this website. We are not implying by it that a group is weird and fanatical and the kool-aid is on the way. Nor are we using it in the sense the Christian community often does, to mean that a group holds outspoken unorthodox doctrine.1
We use the term in the sociological sense,2 to refer to groups that have a specific set of characteristics: they are authoritarian, legalistic, punitive, and exclusive. And you can't leave without incurring dire spiritual consequences. In particular, we are concerned with Bible-based groups that function in this manner.
Many of these groups appear to hold quite orthodox doctrine, and may be accepted by the wider Christian community as one of themselves. However, the cultic characteristics produce an emphasis on performance to gain full acceptance by God, which compromises the gospel of the grace of God in Christ.
The performance requirements differ from group to group. It might be keeping the Sabbath. In another group the individual must be dedicated to personally pleasing and obeying the leader. Or, as in the Geftakys Assembly, you must strive very hard to gain the Inheritance.
In cultic Bible-based groups, believing the gospel and trusting Christ are not enough - there are these other things one must also do to gain peace with God.
2 "Sociological definitions of the term...include consideration of such factors as authoritarian leadership patterns, loyalty and commitment mechanisms, lifestyle characteristics, [and] conformity patterns (including the use of various sanctions in connection with those members who deviate)." Ronald Enroth, ed., A Guide to Cults and New Religions, Downers Grove, Il., InterVarsity Press, 1983, p. 14.