Think of it like this....
We know that the XBox can launch only one XBE at a time.
When we browse anything on our computer, say a Samba Share, Relax Share, FTP connection (with exceptions), we have had to execute one XBE already, in this case XBMC. We use XBMC to THEN launch SMB as a service which also allows us to access remote shares. If you then wanted to execute an app on a remote share, be it XBMC, a Game, whatever, you would be launching a 2nd XBE, which cant happen, becuase you need the Samba share thru out the duration of the time you run the app or play the game. If XBMC stops, which in turn would stop samba, then you cant 'stream' the app anymore. If it were possible to launch samba or relax in the BIOS, kinda like the FTP in the Xecuter BIOS a few months back, then it may be doable.