We've gone from nearly a dozen scrappy hard drive companies to three huge ones. This is what happens when a product stops being cutting edge, and becomes just one more component. (See also: LCD panels and flash storage.)
Graphic by Chris Ritter
Update: As a few comments have pointed out, Hitachi GST also purchased IBM's HDD business in 2003. Also, LaCie is not an OEM source for hard drives, but manufactures enclosures and is an important brand name on the consumer side.
