As GP said, read Christensen's "Innovator's Dilemma". He's the guy who first came up with the term "disruptive innovation", and it's more than just a TechCrunch buzzword -- there's a whole theory behind how disruption actually works.

The concept dates back much further than Christensen. See http://en.wikipedia.org/wiki/Creative_destruction

Schumpeter should be required reading.

Agreed. I was thinking the same thing.