After going crazy on figuring out why my iphone 4 was draining a few percentage points per hour, I figured out that it was because I had WiFi on along with the regular phone being in standby. When I turned the WiFi off, the battery didn't even drain 1% over night. Before you ask, yes I had the "Ask to join networks" options turned to off. Someone in another thread is theorizing that the WiFi connection on the new iPhones/iOS 4 is persistant even when in standby which is why the battery drains. I'm not sure about this but I know what I've seen related to battery drain. For those people with battery drain problems in standby, please turn WiFi off and let me know if this solves your problem. I'm curious if it is global or just specific to my hardware (ie wireless router setup).