Off-topic: Maybe it’s you, not the Internet
Scott Berkun has (yet another) fantastic article on his blog: a teacher was complaining that the students use Facebook or check their e-mail in class. Scott’s response? Maybe it’s the teaching skills and the fascination with one-way lecturing, not the Internet, that’s at fault. Read the whole response; if you’ve been faced with too many narrow-minded teachers in your life, you’ll enjoy it as much as I did.
Of course you have to ask yourself why someone would attend an expensive course and decide to drift off. It could be that he was sent there by someone else (happens most of the time), that he's only interested in a particular topic or that the instructor simply forgot to make a break (my usual sin).
Anyhow, whatever the reason is, it usually proves that you can only be successful if you have motivated students (whether the motivation is theirs to start with or you manage to motivate them) and that long one-way lectures are not the best way to teach people