You might not think you're a heavy user, but you are. Especially if you use those apps on a consistent basis.Are you kidding me? No more then 3GB a month? Let's look at some of the basic things that the phone can do while having no access to a wifi connection:
Siri
GPS
Pandora
Netflix
Safari
YouTube
iCloud
I think you get the point. The iPhone is capable of tons of different things that all need data. Bandwidth consumption is bound to increase due to the way technology is progressing whether we like it or not. I can't imagine not hitting less then 2gb every single month and I feel like I am not even a heavy user. That's why I pay for UNLIMITED.
I mean, I could care less. Use away. It doesn't hurt me at all. But if you do use those services often, you likely fall into the top 5%. And that puts you on AT&T's little list they generate.
I use my phone a good amount. I use Maps like crazy when I'm on the road. Safari a bunch. FB, Twitter, a bunch of push notifications. Email at least two to three times an hour. Words with Friends, iTunes. Pandora, NetFlix, Youtube, yeah yeah. I've never gone over 1.8 GB, and have only exceeded 1 GB two other times in the last 15 months. Because when I get home I'm connected to wifi. Sometimes at work I'll hop on the wifi. Coffee shop, hop on the wifi.
Again, if you don't have a wifi connection at home I could understand... and in that case you don't have much of a choice. I could ring up well over 3 GB if I didn't have internet at home.
At the end of the day, the Thread Starter needs to decide if he wants to pay significantly more for data that won't be throttled. Simple as that.