Steam has delivered approximately 10 million gigabytes of data since the first of the year. You could fill 125,000 80 GB hard drives with this data to make a line over 11 miles long. Not that you would want to, but the visual helps.
There have been a total of 50 billion player minutes in our multiplayer games since the start of the year. If a single person sat down to play on their own, it would take 2.28 million years to accomplish this. This is assuming that you're not planning on sleeping during this 2 million year stretch.