I think it might have been AdBlock Plus, or maybe this Connections Optimizer setting in the phone (an option available under Mobile Networks).
I think either the Connections Optimizer was screwing it up somehow, or maybe AdBlock Plus and the way it filters what with the proxies and all... I have AdFree installed now. I didn't download any games at all and I haven't used the GPS since I've had the phone. Mail sure but mail checking should not eat up this much data. Especially since I was on WiFi...
On a side note, Root App Delete seems a wonderful thing to have. I can get rid of a lot of stuff that came with the phone that I don't need/want/use. Even the Connections Optimizer.