There are LOTS of non-smart phones out there that don't require a data plan. You just have not looked. The ability to get on the internet is NOT the defining ability of a smartphone. Feature phones have been able to do that for a long time...
But the high end of the smarts still aren’t that big, iPhone is at under 5% of the handheld market.
You are wrong in your "under 5%" of the handheld market. In the 4th Quarter of 2011, Apple's world wide share of ALL phones, smart and non-smart was 8.7%... and it has climbed since then. In the last quarter, Nokia was knocked out of 1st place... and Apple has climbed. It is over 9% but less than 10%. Your figure was accurate in the last quarter of 2010... way out of date for a company growing now at a 120% year over year average rate each quarter.
As far as I’m concerned if it does anything more than make phonecalls and texts it’s a smartphone. Maybe not as smartphone as other smartphones, but I did make the distinction between the high end and low end of the market.
According to here http://www.pcmag.com/article2/0,2817,2395951,00.asp#fbid=SLgcdJun7IU Apple has 4%. And that’s Nov 2011.