It's estimated by the US Center for Disease Control that 20.2% of US households are now wireless only. The major carriers are seeing their wireless businesses boom and their traditional wireline businesses decline at an accelerating rate.

In its recent quarterly earnings announcement, AT&T de-emphasized its wireline losses, disclosing them in SEC filings but offering little specific detail in the investor release and slides.

From the investor release from Q1 2009:

Total first-quarter wireline consumer revenues were $5.4 billion, compared with $5.8 billion in the year-earlier quarter, as declining voice revenues more than offset growth in video and broadband.

Here's what the 10Q filing said about wireline losses (in millions):

Our wireline segment operating income decreased $809, or 27.4%, in the first quarter of 2009. Our wireline segment operating income margin decreased in the first quarter from 16.7% in 2008 to 12.8% in 2009. Operating income continued to be pressured by access line declines due to economic pressures on our consumer and business wireline customers and increased competition, as customers either reduced usage or disconnected traditional landline services and switched to alternative technologies such as wireless and VoIP.

Local voice revenues decreased $632, or 10.8%. The decrease was driven primarily by a decline of $501 attributable to a decline in access lines and by a decline in revenues from AT&T Corp. (ATTC) mass-market customers of approximately $40. We expect our local voice revenue to continue to be negatively affected by the slowing economy and increased competition from alternative technologies.

• Long-distance revenues decreased $517, or 14.2%. The decrease was primarily due to lower demand for long-distance service from global and consumer customers which decreased revenues $369 and expected declines in the number of ATTC’s mass-market customers, which decreased revenues $148.
• Local wholesale revenues decreased $62, or 15.4%. The decrease was primarily due to declining number of Unbundled Network Element-Platform (UNE-P) lines sold to competitive providers.

GigaOM points out a campaign to "scare" AT&T customers into retaining landlines for emergency purposes. There is a valid point here, but it's being exploited for customer retention purposes.

Last week Verizon sent a letter to non-Verizon customers encouraging them to "cut the cord" and ditch their landlines in favor of a Verizon wireless plan. Verizon, too, is losing landline customers. 

The following data are from our recent consumer survey. The number who've given up their landlines (16%) is lower than the CDC number because this includes Canadian responses, where users are more likely to retain their landlines. 

Source: LMS/Opus Research (n=707, April 2009)