Wow...I go over my 5gb all the time with limited streaming. I go WAY over when streaming events like snow storms, while geocaching, or various news conferences and events. Of course I also stream with live audio, chat and high quality video as much as possible, via a internet based site which likely isn't as thrifty as the chase related stream sites.
I'm not sure...but I believe some carriers have open source type situations. I know that a buddy uses a sprint datacard (598U) on the verizon network. I guess that may not be likely with AT&T on a different system, but always checking out the full options is good when you need to keep an unlimited plan...which I highly recommend, especially as the need increases every year.