Is this Apple's version of Fight Club?
"The first rule of iPhone SDK is, you do not talk about iPhone SDK."
Jokes aside, make it known that anyone attending an iPhone session
must have downloaded the SDK and agreed to the NDA. That should cover
all of the legal bases.
For what it's worth, I sent a quick note to Aaron Hillegass as well.
Considering Big Nerd Ranch has iPhone Developer classes scheduled for
September, I'm sure Aaron & co. would know what's going on with the
NDA.