I could care less about DVD playback for the Wii. I have a great DVD player that handles DVD+/-R discs as well as DivX files. I wouldn't be surprised if Nintendo made the Wii incompatible with rewritable discs in order to combat piracy, which would exclude about half of my movies.
A one million digit friend code sounds like a pretty outrageous rumor to me. Nintendo will make online play as easy to do as they possibly can while still ensuring that it is a "safe" experience. It would be foolish of them to do something that makes it impossible to play with friends online. Let's face it, between Microsoft, Sony and Nintendo, it seems like Nintendo is maintaining the strongest focus on pleasing the customer. If nothing else, you can trust that the Wii will be easy to use.