Is it just me, or is some of the math way off here?
First, volume of the punch cards. Wikipedia gives the dimensions of an 80-column IBM punch card as 187.325 x 82.55 x 0.18 millimeters. Multiply that by 15 x 10^18 bytes, divide by 80 bytes/card, and converting units, I get 521.9 cubic kilometers. The area of New England is 186,458.8 square kilometers (Wikipedia again), so it would be covered only to a height of 2.8 meters.
Second, the commercial hard disk industry must ship far more than "8 exabytes worth of drives annually". That would only be 8 million 1TB drives. The PC industry ships hundreds of millions of units annually, and 1TB is a smallish drive nowadays (for desktops at least).
...Ah, I think I see the confusion. The cited article
reports that "total disk storage systems capacity shipped reached 8.2 exabytes". However, this appears to refer to a single quarter of 2013, not an entire year. More importantly, "disk storage systems" here probably refers to high-end managed storage servers, not raw hard disks. (A chart on that same page lists EMC as the largest vendor; EMC doesn't manufacture hard disks.)
Edit to add: according to a random research report by IDC, projected drive production for 2014 is 300 exabytes of capacity. Take this with a grain of salt, but it seems like a more plausible order of magnitude.
Edit to add^2: Wikipedia reports the land area of *Boston* as 125.4 km^2. Dividing 521.9 cubic kilometers of punch cards by this figure gives a depth of 4.16 kilometers, much closer to the 4.5km figure in the article. The remaining difference might come from the fact that I did my math directly on the size of an individual card, without allowing room for boxes.