Some people work with terabytes. Most work with gigabytes as their largest standard unit of data storage measurement. To get to an exabyte, first take a look at the 100GB flash drive sitting next to your computer. Now, imagine 10 million of those. That's an exabyte.
Where in the world is all of that data stored? What about the emerging data - if the study goes through 2007, surely it must be much more than that by now?
Take a look at this graphic by Mozy  to get a better understanding.