The number of households in the United States that rely solely on mobile phones continues to increase. As of July 2011, 31% of households had mobile phones and no landlines. Additionally, almost one in six households used mobile phones exclusively or almost exclusively, despite still having a landline.
http://robertsiciliano.com/blog/2013/04/09/why-are-cybercriminals-moving-from-pcs-to-mobile-devices/