An Australian perspective, and possible solution
I am an IT professional. I got burned with excessive data downloads and you could say I should have known better, however even the best of us have troubles keeping up with every change. Two changes got me.
I live and work within a 5 km radius of Melbourne's CBD (Melbourne is our second largest city). I allow data downloads through 3GS and also allow data roaming. When I leave the CBD I turn these off.
However with the advent of iCloud I allowed some backups and made sure they occurred while I was asleep when I was in my house with WiFi running. Unbeknownst to me at the time, the iPhone turns off WiFi when it is in hibernate mode, but it still allows data transfer. You can see the outcome.
Secondly my provider merged with Vodaphone, and it appears to be progressively shutting down the original network. The result was that I got new data roaming charges while living, working and commuting within 5 km of my CBD. Something that never used to happen.
In the first case we get notified by the ISP when our bill is 5 times the average, this is many hundreds of dollars and an outrage. I did go to our Telecommunications Ombudsman over further charges but couldn't negotiate a reasonable cost beyond my first notice of many hundreds of dollars, but at least it wasn't thousands like you sometimes read of.
In the second case I decided I had enough, and now I have a pre-paid sim with another supplier. With this I have total control over what I spend and I do not get a massive cost blowout. The cost and convenience of my pre-paid package is comparable and in the case of data a lot more affordable.
So I suggest everyone look at pre-paid packages as it is the only way to avoid the attrocious highway robbery of the post-paid schemes. I disagree with the proposition that this is an education issue. Post-paid schemes are a license to rip people off, whether they are technically literate or not. Which reminds me I must buy more Telecoms stock.