Streaming-based services such as Amazon, Netflix and Blinkbox (owned by supermarket giant Tesco) let you subscribe on a month-to-month basis or film-by-film basis. These services feel more flexible because they're not trying to sell you a whole bunch of channels, some of which you may not have much interest in.
Interestingly, even the BBC can see where the market is heading for many viewers. Their "youth" channel BBC Three (aimed at 16-34 year olds) will stop broadcasting terrestially and become an online-only channel via their iPlayer service. I guess this reflects how more and more people consume content today - they don't consult a TV schedule, they expect to be able to view content when it suits them.
Regardless, it is silly to argue right now that Netflix/Hulu are the primary causes.
I'd absolutely be a cord cutter if it weren't for cable NFL games and Syracuse Basketball.