The number of 'internet only' TV homes in the US rose 23% Y-o-Y in Q3 2011

"Characterizing it as a “development to watch,” Nielsen issued a new report to clients Wednesday showing that the number of U.S. households that bypass cable or satellite TV and subscribe only to broadband Internet access has grown dramatically in the past year, and not surprisingly, they spend dramatically more time watching TV over the Internet.
The Nielsen report said it is too soon to determine whether these households are so-called “cord-swappers”  - swapping the cable/satellite TV cord for the broadband Internet cord - but they are growing faster than any other segment of the “cross-platform” television marketplace.
While the percentage of Internet-only TV homes is still relatively small - less than 5% of all TV households - they grew 22.8% over the past year, according to the report, which reflects data for the third quarter of 2011 vs. the third quarter of 2010."

Source:  MediaPost, 9th February 2012