I've started to see a lot of iPhones around campus where I'm at and asked a lot of people why they got theirs. It's word of mouth about the easy upgrade from an iPod. At least 50% had their iPod die for some reason or another and decided to spend the $200 on an iPhone instead of a similarly priced Nano. Especially people who always carry both an iPod and their cell phone around all the time. It's not the direct marketing but more of a coattailish the "I have to go to the Apple Store to buy a new Nan... oooohhh! shiny iPhone" factor. It's just my conversations, your mileage may vary. (Also 'daddy' pays the $30/mo, so it's a non-issue.)
All the extra features like games from the App Store, Google Maps, GPS, and other junk this list goes through just sweeten the deal.
Marketing spurs every single American to buy hundreds or thousands of goods per year, and not once has anyone ever realized they bought one due to marketing. When asked, not a single one would ever cite a commercial.
I hate it when people quote the $70/mo. Do you not pay for a regular cell service? If you actually look at the numbers, the pricing is exactly the standard AT&T plans + $30/mo unlimited data plan. (If you can get regular AT&T at a discounted rate, even better!)
I currently have T-Mobile prepaid and average about $10/month. I really want the iPhone, and can easily justify spending $200 for the device, but I don't want to be locked into a 2-year contract paying $70/month (totaling $1680) when my needs are met with a much more modest price.
All the extra features like games from the App Store, Google Maps, GPS, and other junk this list goes through just sweeten the deal.