According to an article in The Atlantic, The Seven Signs You're in a Cult, there are some signs of the more serious implications of belonging to some kind of religious-style cult (the kind were members occasionally end up dead) that don't seem to fit WikiTree--even if you squint your eyes and make adjustments to the religious angle. The kind of cults we tend to hear the most bad press about, after all, tend to be the religous cults. And when things go wrong with them, the fallout and damage can be especially bad.
So the seven signs mentioned in The Atlantic article are: (1) Opposing critical thinking, (2) Isolating members and penalizing them for leaving, (3) Emphasizing special doctrines, (4) Seeking inappropriate loyalty to their leaders, (5) Dishonoring the family unit, (6) Crossing boundaries of behavior, and (7) Separation from the Church.
I'd say WikiTree in some cases actually embodies the antithesis of these seven signs, since Wikitree actively encourages critical thinking, and actively honors the family unit.
And as for the other signs, I'd say WikiTree seems to me very respectful without demanding inappropriate loyalties, and very open to members coming and going as they wish to do.