You have to be careful when talking about big sweeping technological change in home entertainment. Every time you can watch something neat on an Xbox or the web, you get the feeling that everything else, like cable TV, is getting ready to be swept aside. The truth is that cable is crushingly dominant in America today, it has a lot of power, a lot of money, and a lot of the content that people want to see.  

With that disclaimer established, however, it is notable that a growing number of people really are dumping cable and getting their shows through other means (because we need shows).

Mashable cites a new report:

From 2008 to 2011, the Convergence Consulting Group estimates 2.65 million — 2.6% of the U.S. population — ended their pay-TV subscriptions and replaced them with online streaming services such as Netflix. More than 40% of U.S. pay-TV subscribers became non-subscribers by dropping their service in 2011.

The report also showed that new subscriptions are still coming in for cable but at a lower rate than people are dumping cable. Ad sales are up for for online content as well.