Those Treo's are pretty. Which network is it on? T-Mobile?
There are still a lot of phone companies charging monthly fees for data usage, but that is going to change in the next year. Sprint/Verizon already have all you can eat packages, and as they start to realize that the money is in selling things, not bits, they will change.
The Sprint Treo is even fairly highspeed by comparison. (up to 56k, instead of 14.4 that you get on AT&T/Cingular/T-Mobile).
That being said, I think the market is starting to pick up. As an example, Sports Illustrated is selling their swimsuit models as background images for phones (using a system I designed at my former employer), and several large soft-core sites are investigating similar solutions.
Check out the SI site: (not that I would pay 2 bucks for one photo, but what the heck, people are strange)
http://si.fuelshop.com/ 