What do you call a ‘cult’?

Cult? Sect? New Religious Movement? Alternative Religion? The terminology used to describe some religious groups and movements is confusing — in part because the words used are ambiguous.
In his column at Patheos, Christian theologian Roger E. Olson addresses Safe and Unsafe Sects (and Problems with Terms for Alternative Religious Groups). A good article, though the mention of J. Gordon Melton does inspire us to provide a word of caution regarding cult apologists.