What a pointless question. I don't think it's impossible he's faking it and that these people are actors. There is no evidence of it, nothing he's done is for a fact impossible, and really at this point in his career I think someone would have talked by now. One of the countless conspiracy theorists or reporters who don't like him would have found a single piece of evidence...
I think it's more likely that there are those that could never pull off his work and don't understand what he does. They decide their own incompetence or limit to their knowledge is impossible. therefore, actors.
Derren claims that Channel 4's lawyers would not let them mislead the public into thinking someone was a member of the public when they are really an actor. I guess maybe he's making that up too?
I'd be interested in any evidence showing the highlighted part to be true.
I have no inside information on Derren Brown. These guys seem to think at least one actor has been involved: http://shockradar.org/2012/10/29/it...s-apocalypse-star-revealed-as-aspiring-actor/
But how would we ever know, as long as fakery could duplicate "honest" trickery?
Here's a thread on JREF that talks about Brown using stooges and at least one actress: http://www.internationalskeptics.com/forums/showthread.php?t=228724