What prevents a vampire from careless and frequent use of the mind gift?

Arrogance, Louis had cuttingly suggested. Love, Armand's riposte. It is these things, and more. The mind is complex, fragile, prone to collapsing in on itself when the wrong kind of pressure is applied. It is as good at protecting itself as it is easy to manipulate, and certain minds can close like steel traps over those manipulations unless you know what you're doing.

And Armand does, typically. Like here, tonight, the FBI agents sitting across from Daniel Molloy and asking uncomfortable questions. They aren't night guards or drug addicts or the usual fare of inconsequential people that Armand may snap his fingers and make think or forget this or that, but highly attentive, focused, dangerous.

So he is subtle. Slowly, the questions being asked become shorter. The answers provided from Daniel sink in more readily. They are more certain they're dealing with an uninvolved fanatic, looking for another piece of meat to feed the celebrity. They become sure they are wasting their time. They think it in clear unison, in a silent glance to each other.

One would hope Armand couldn't do this from a long distance away.