In fact, storage-area density apparently increases more rapidly than does transistor density (i.e. Moore's law).

http://en.wikipedia.org/wiki/Mark_Kryder#Kryder.27s_Law

A PhysOrg.com article reports on a 2009 study by Mark Kryder. According to the report, if hard drives continue to progress at their current pace, then in 2020 a two-platter, 2.5-inch disk drive will be capable of storing more than 14 terabytes (TB) and will cost about $40.

Huh? 1tb hdd was released in 2007, 2tb in 2009 and 4tb in 2011. Looks exactly like Moore's law to me though we've been set back by Thai floods of 2011.