According to The NPD Group, market research, consumer sales of smartphones to U.S. consumers represented 23 percent of all handset sales in the fourth quarter (Q4) 2008 compared to just 12 percent in Q4 2007.

Led by the release of Apple's iPhone 3G at $199, the average price for a smartphone fell 23 percent from $216 in Q4 2007 to $167 last year.

While half of smartphones on the market now sold with touchscreens, 70 percent of all models instead offer QWERTY keyboards.  T-Mobile's Android debuted and Palm's webOS will debut handsets that support both QWERTY and capacitive touch.

As the AT&T 3G network construction continues, and T-Mobile's begins, high-speed data is becoming more central to smartphones. In fact, two-thirds (66 percent) of smartphones now use 3G networks, compared to just 46 percent a year ago.

With prices continuing to fall, manufacturers and retailers are looking for ways to bolster sales revenues. One option is to sell accessories, since they can help drive margins for smartphone retailers. In fact, more than half (52 percent) of smartphone buyers purchased an accessory at the time of their phone purchases, compared to just 41 percent among all other phone buyers.