40% of Google Maps usage is through mobile devices

"Mayer revealed that 40% of Google Maps usage is mobile. And Christmas and New Years day had mobile usage of Maps surpass the desktop — which is a first for Google products. Google Maps now has 150 million mobile users. To put that in context, Maps for mobile had 100 million users in August of last year."
Source:  Marissa Mayer of Google, speaking at SXSW, reported by Techcrunch, 11th March 2011