I have read an excellent book about the full history of magic called, oddly enough; The Illustrated History of Magic. It is a big read at almost 500 pages but WELL worth it if you are interested in more than just tricks. This book is, in my opinion, the definitive history of magic, the most comprehensive I have found. It is, of course best to have the hard copy to read but it is available in its entirety at
http://books.google.com/books?id=gsvLtLFKFvgC&lpg=PP1&pg=PP1#v=onepage&q=&f=false
Nope I am not trying to be spam, I have a point.
From what I can recall, there has never been anyone killed just over a trick, or secret. Even back in the 17 and 1800's magicians were not a dangerous crowd. I would certainly say that many magicians have probably been shunned from the community, and for anyone that IS passionate about magic being shunned can be very damaging.
As far as the Penn and Teller thing goes; the information was out there for anyone that wanted it, the problem though was it being broadcast on television for the layfolk to see. Posting tutorials on Youtube is one thing but broadcasting it on television is a whole different game.
I would assume that Penn and Teller felt it ethically 'safe' to do such a thing because cups and balls is an ancient routine and has been done in about every context conceivable.
Honestly, I feel like the only magic that should be exposed on television is party trick type stuff, like any oldschool tv magic special would do. the 'masked magician' though, I am not so cool with alot of the stuff he reveals.
While I guess I do agree with the censorship of magic on television, youtube for me, is another story. When it comes to people revealing magic my opinion is that if it is being sold then you should expect it to be revealed, times have changed. If, on the other hand, someone were to reveal someones original effect or method and the originator did not consent to it I am completely against it. If the originator intends for it to be their own trick and is not trying to make it public it should not be revealed, even if you figure it out.
But, yes here is where the But comes in. In my opinion, if the originator is selling the trick TO THE PUBLIC, they should expect for it to be revealed. In the day and age that we live in now, any information that is ever made public in any way has a very good chance of getting on the good 'ole interweb.
I think the question comes down to: The Magic Community versus The Layfolk. Revealing a method to everyday spectators is VASTLY different than revealing things to the community of people that are so interested in the information that they would proactively seek it out.
Oh, and the main point. Just as I said earlier: magicians just arent that dangerous of a crowd.
