Yeah, file sharing on mobile isn't quite at the Bittorrent level yet, although with Wi-Fi becoming more popular, you'll be seeing some more Zune-style stuff happening. Memory's getting bigger, what with 32 GB SD cards in the works from Toshiba, and as network speeds increase with WiMAX and other 3G fun, P2P applications could very well go mobile in the nearish future. For now though, it's just a pipe dream.