As the questions mounted in the hours after the launch event, Microsoft issued the following statement (via the site of Xbox Live head honcho Larry "Major Nelson" Hryb):
We know there is some confusion around used games on Xbox One and wanted to provide a bit of clarification on exactly what we've confirmed today. While there have been many potential scenarios discussed, today we have only confirmed that we designed Xbox One to enable our customers to trade in and resell games at retail. Beyond that, we have not confirmed any specific scenarios. Another piece of clarification around playing games at a friend's house -- should you choose to play your game at your friend's house, there is no fee to play that game while you are signed in to your profile.