There is another important question with regard to geneivas daas; magic.
The magician acts with sleight of hand. He seems to perform one way when in
reality he is doing something else. The Rambam writes that certain types
of sorcerers perform various tricks, such as putting a piece of rope in his
clothes, and coming out with a snake. He writes that this is geneivas daas.
It is possible to differentiate between the Rambamís case and magic of
nowadays. In the Rambamís case they were performing real kishuf (sorcery),
whereas nowadays it is merely sleight of hand. However, the Bach writes
that even when there is no real sorcery, magic is forbidden because people
believe that he is performing genuine magic.
Nonetheless, it seems that one can still differentiate between the cases
above (where there was genuine kishuf or where the magician pretends that he
is performing kishuf)) and when the magician begins by announcing that he is
not performing real magic, and it is all illusion. In such a case, it
seems that even the Rambam would allow this. Rav Moshe Feinstein and indeed
paskens in this way. For anyone considering a career involving magic, it
is strongly advisable to discuss the issues involved with an Orthodox Rabbi.