Not to mention blowing through your entire battery running the radios to stream what you could just as easily sync.
If you really want to stream your own collection over the WAN, there are already NAS appliances and streaming applications on the market that can deliver the goods. And if Apple prices this like their completely underwhelming Mobile Me offering, those alternatives could end up being a lot cheaper.
go look at the pandora app. i don't see anyone complaining about that. This would essentially be the same thing except every song would be of your choice bc it's YOUR music.