I have a bluetooth USB dongle with a LED indicator which is blinking slowly
when it's active. 
If I disable it via KDE desktop applet by unchecking "Enable Bluetooth"
checkbox, all bluetooth devices are disconnected, but dongle itself stays
flashing, even when PC is shut down or put into suspend mode. This is very
annoying behavior, as it lights up the room in the night.
However, if you go to bluetooth settings window, and uncheck the 'Enabled'
checkbox for a specific bluetooth adapter, it goes down completely, no LED
blinking.
The applet checkbox used to bring it down long ago, but it got broken at some
point.