I really have no idea what kind of background processes. It was probably a whole lot of stuff since I had not killed any processes since I restarted my phone. But I wouldn't think it would have been anything demanding data.
I've had the phone since launch day. The battery life never has been too good, but I've never noticed a huge drop like this before. And no, I haven't installed anything new in a couple days.
The coverage around my house is perfectly fine. I usually have anywhere from 3 bars to full coverage in 3G.
I don't have it to where it automatically updates emails. I never receive notifications for new emails.
I don't have a bunch of widgets running either. I've got the News/Weather/Calendar widget, the Social Widget, ESPN Scores widget, Google Voice, and the Weather Channel, and all of those don't update on their own except for Voice (which wouldn't have been updating).
GPS was off. Wifi was off. It was running off of 3G with the Sync setting turned on.