Thanks to innovations like PDAs and the iPad, the internet has formed an enormous relationship with the searcher-on-the-go. It's no longer necessary to search for recipes, directions, store locations, or anything else prior to hitting the open road, and many internet users today are taking full advantage of having a world of information instantly accessible at their fingertips.
While mobile advertising is set to close out 2010 at around $743 million, expect that number to hit $1 billion sometime in 2011 (2009 was substantially less "mobile", at $416 million.
We have Apple's iAd and Google's AdMob to thank for the spike in revenue. Also in correspondence with the mobile frenzy, it now seems that sometime next year, there will be more web-enabled smart phones than basic feature phones. Because of the huge popularity of mobile search, it is truly in a company's best interest to have their site available in a mobile friendly version.
You can read more about the future of mobile here.