For everyone that's bitchin about it, he's only charging $6 and the book is definitely a good read. If you don't find 1 idea in there worth the $6, then you're in the wrong business. Even if all you got out of it is a little motivation, the book was paid for.
How often do you spend $6 (most likely much more) at the bar? Or on pointless stuff from the store? Probably multiple times throughout the week. Those things don't make you any money or give you ideas, yet nobody complains there.
And about him having my address, so what? If he wants to mail me some shit for free down the road, then whatever, it isn't doing anything to me.
He also can't just charge your credit card later on either, as that would be against the law and I don't think he would risk going to jail to charge a bunch of people's cards out of the blue one day.
Regardless of which way you look at it, what he did is a brilliant idea for the reasons several others pointed out. He has basically pre-sold thousands of copies of his book already, which means when the full version is released, he has a rough idea of how many people are interested in it. On top of that, he's got numbers to show potential publishers. And he also increased the size of his list even more.
Whether you like Frank or not, just watch what he does and you will see he's a really clever marketer. Even if you don't buy anything from him, use his strategies in your own business and see how they work.
I've personally never bought any of his courses aside from a free trial to something he had. And then I also bought this book. So no I'm not one of those "Frank Kern fanboys", but I do like his style and I think he's a smart dude for sure.