Bingowings said:

The machine needs to be logged into the account to identify the game is being used by the authorised user.

So you can switch off the console but you can't play any of your games on it unless you are online and logged in.

If you get banned or the service is closed the machine becomes a brick.

“There are many devices in your life that require the Internet to function,” he said. “Xbox One is no different in that it requires, at some point in the beginning and at various times through its on state, to connect to our cloud and to our Internet. That is to deliver Xbox Live functionality, that is to deliver download content to you, that is to deliver some of the innovations around TV and entertainment that we showed today. But it doesn’t require it to be online all the time.”

Totilo then asked him how often it checks your connection, and the response was “Depends on the experience.”

“For single-player games that don’t require connectivity to Xbox Live, you should be able to play those without interruption should your Internet connection go down. Blu-ray movies and other downloaded entertainment should be accessible when your Internet connection may be interrupted. But the device is fundamentally designed to be expanded and extended by the Internet as many devices are today.”

The thing that stinks is that so far the evidence is pointing toward them charging you to play used games. One of the Microsoft officials stated that if you try to use your buddy's disc they'll charge you full price before you can do so. That also would erase the game from your buddy's account.