Sorry for being grumpy, but how does it help to say that "1 petabyte = 20 million four-drawer filling cabinets filled with text"? Changing one huge number (1pb) with another (20M) doesn't add much to the overall understandability. The other examples are similar in nature. They're either comparisons with other giant magnitudes (10B facebook photos) or comparisons with things we have no fucking clue of how big they really are (HD manufactured in 1995, google's processed data).

"1 petabyte is a lot of data". Oh rly?