What is the Size of the Universe?

When I first made the Hubble Deep Field: The Most Important Image Ever Taken video, there has been a consistent avalanche of comments stating that there is no way the universe can be this large. Figuring out the size of the universe isn't as simple as just multiplying the distance light travels in one year by the age of the universe.
We need to account for the expansion.
Astronomers have recently estimated a lower limit to the size of the universe to be roughly 78 billion light years in diameter. In this video I try to explain how that's possible.
For the more technically inclined, here's a link to the scientific paper this vid is based on:
All music used:
Leonard J. Paul - The Corporation Soundtrack:
iambic2 - under these stars, we'll sleep again:
Kevin MacLeod - Truth of the Legend