Seeing as song sharing is such an important piece of the Zune puzzle, we thought we'd show you again what the Zune to Zune file transfer looks like. You'll notice that it's quite speedy to send a song, which then kicks you from whatever it is you were doing into your Inbox to view what was sent to you.
Brian thinks the transparent popup notification is obtrusive, and on one level I agree. But there's pretty much no way of sharing songs by asking for permission without prompting the user somehow. Just be prepared to turn off your wireless if you don't want random people sending you things.