I think you're right. I'm guessing that if you send it to free.kindle.com it will only deliver over wireless (not 3g). If you use kindle.com, it will also deliver over 3G, too. That's a moot point for people like me who only have wifi. It would be something to be aware of if you have a 3G/wifi model. I've also been using kindle.com to send about 20 books, with no charge, and my limit is 0.00. Hope the charges don't show up
