HARLEYHOBO--YOU SAVED MY LIFE! I have no idea how I stumbled across this forum and your message--fate, luck, whatever, but thank you! thank you! for posting.  I had the old 3G for 5 years, and just now bought both my husband the 3GS, and myself the 4.0.  In all the reading I've done, and other people I've ever talked with (and I know a lot of iphone users).  NOBODY knew about or how to use this "tricky" little feature.  When I saw your message about closing the apps and the minus button, etc....I nearly fell out of my chair.  I know right then!  That's it!!  Well, most of it.  Add in the fact the the new phones have video and games, features far above what the old phones used, but heck, leaving those running in the system tray is a HUGE data eater--if you you've got a FaceBook upload going on, or some random location user app running.....anyway, I wonder, did you track your data further?  And, was this the main culprit?  I am starting my data tracking today. 

I'll say one thing, however, I'm not normally a conspiracy theorist, but why is that with so many complaints and so many people that have iphones, do so many people not know about this very important, very tricky, very COSTLY feature of the new software/phones?  It wouldn't be that someone has alterior motives would they?  I'm sorry, but this one smells like underhanded dealing - and even Apple is looking pretty bad on this deal......

Thank you again!!