Do you take your computer with you everywhere? The point is to bring back the days of "take a DVD over to a friend's house to watch it there." (Funny how we lost that bit of convinience in this online video revolution.)
This presumes your friend has an AppleTV, but at $99 the chances of that keep getting greater every day.
Even if the friend doesn't have an Apple TV, it's so small that anyone can take theirs anywhere they go. Even if you don't have an apple tv anyone can buy the cable that connects iPhone to a TV. Almost same thing.