I've been having the same battery drain / occasional heating issues as other people, with Wi-fi Sharing popping up in the battery usage statistics. I managed to improve the battery life hugely by turning off background data, auto-sync, GPS, bluetooth etc. Found I really needed background data on (for things like Android Market) so yesterday re-enabled this. Used the phone as a GPS on the way home, all fine and didn't get too hot. Battery drain overnight was pretty good, 90% down to 82% as you can see, and Wi-fi Sharing didn't rear its ugly head. I then used the phone this morning to check emails, Facebook and BBC news, browse the internet, download and play a music WAV file. I noticed the phone getting hot and checked the battery again - down another 20%, with Wi-fi Sharing right back up there! I wasn't doing anything strenuous on the 'phone, but it seems something triggered the Wi-fi sharing which then maybe got stuck in a loop and used up a lot of the battery. I was able to force it to stop, and things calmed down again. Has anybody found out what causes Wi-fi Sharing to come up? I don't particularly want to root the phone (I didn't even jailbreak my iPhone) but this is ridiculous. I'm on Gingerbread KE7 I think.