Naturally, this is not going to hit everyone in the mobile market. Even in the United States, the smart phone penetration rate is only 56 percent (check http://en.wikipedia.org/wiki/List_of_countries_by_smartphone_penetration); but does it really matter?
If this approach only reaches 56 percent of the market at best, is it truly an appropriate solution? Yes, but how can this be? The following two reasons explain it best:
People who do not have a smart phone don't usually have a data plan. Surfing the web becomes financially prohibitive. Most people without smart phones and data plans won't be reaching you.
People who have old smart phones like BlackBerry 5 or earlier, may have a data plan. However, those devices have browsers that are barely worth the name and their users know it. They might hit your site, but it's not likely, and their existence is dropping quickly.
It's likely that almost anyone who hits your site with a smart phone will respond as...