"Cheating?"

A couple in India have been charged with cheating thousands of people who believed that they could perform effective magical spells. The couple apparently charged substantial fees for spellcasting and their notoriety spread mostly by word of mouth.

`Black magic' Woman, Husband Held For Cheating

Interestingly, though, the article does not really explain how these individuals actually cheated their clients, implying that anyone casting spells for money is automatically a fake. While this is true more often than not, if the spells really worked one would expect the casters' fame to spread by word of mouth without deceptive advertising - which is exactly what seems to have happened in this case.

Maybe they were getting good enough at making things happen that someone important was starting to get worried. You can never be sure.