Bluetooth keeps turning itself on

My brand-new MacBook Air (2011 11") has never been connected to anything Bluetooth. Neither had the previous Air I migrated from. I never use Bluetooth, although I do plan to get start using a Magic Mouse occasionally.

BT was on out of the box, but I turned it off. I intend to keep it off all the time except for certain future mouse tasks.

But several times a day I notice it has turned itself back on! I turn it off, but it never lasts. (I keep the BT icon in the menu bar so I can watch the situation.)

Any fixes? I don't want any needless battery drain.

Thanks in advance!

(Also, I notice that the Prefs checkboxes that bring up BT Assistant when "no keyboard [mouse/trackpad] is detected" cannot be turned off. No big deal--the assistant never appears anyway, since obviously a laptop can't have that situation! But I still thought it might be a related symptom: when you uncheck either option, a confirmation sheet drops down. But it doesn't matter which choice you make on the sheet, the boxes stay checked.)