Personally I think that mobile phone data plans are a huge white elephant, despite the fact that the cell phone companies have invested billions in them. Here in the UK the mobile phone companies actually paid off our national debt a few years ago with the billions of pounds they paid for the 3G licenses. Very few people are actually using 3G data plans.

The future for Internet on the go will probably be discreet wifi zones -- simple but effective, and a lot cheaper than most phone data plans (and faster, and more reliable). Of course, Wimax will simplify all this.