Google states that in the UK (May 2003) 73% had researched a product or service on their phone.
We are two years on from those stats now and the use of tablets and smart phones grows continuously.
"Google Search will be expanding its use of mobile friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact on Google Search results."AdSense
If your business is on the web, then having a mobile friendly (also called mobile responsive) website means you won't be overlooked on mobile devices.