I recently got interested in this problem as two weeks ago my battery drain problems started and it would only last between 1-4 hours, and would take ages to recharge, and the phone was getting hot.
I went to the battery usage in settings and found that the OS was consuming around 70% of the battery. It was being drained rapidly even when in idle. The screen was also becoming hot at the top of the phone, an S2.
I downloaded betterbatterystats and found two processes being run pretty much constantly. They are svnet and svnet-dormancy. They are involved in the sending of data packets. I then checked my current data usage with my provider. This month it has gone from an average use of 40mb per month to 360mb and were only just over half the way through this month!!
So for me what is happening is that a process is constantly sending and receiving data packets. I wondered at first whether this was a faulty app so I bit the bullet and deleted all updates and downloaded applications. No joy. Still the same problem. I then thought maybe its a virus so I download a virus checker. Nothing. Still the same problem. Scratching my head now.
I then noticed the box in Settings/Accounts and Sync/Background data and unchecked this, problem solved. Battery back to normal, no heat problems, no recharging problems.
Whether this is a client or server fault I don't know. I have google/yahoo/facebook/exchange server account settings. I know of five people personally who have been affected by battery drain issues within the last month. I don't know why. Two have sent there phone back for repairs. Others are looking at exchanging their's for an iphone.
My temporary fix may not be the answer for everyone but it explains why the battery is draining so quick, why the phone is getting so hot, and why it takes so long to recharge.
On a side note, why is the android OS so user unfriendly to upgrade. You go to the settings/software update/check for updates (mine is android 2.3.3) and the phone says no update available, yet i know android 4.? something exists. Can someone point me in the direction of how you upgrade the OS. Thanks in advance.