I agree, it's still best (safest) to be sure the transmitter is always on while the receiver is on.

The new 2.4GHz radios (like Spektrum/JR) have failsafes built in to keep bad things from happening if the transmitter is switched off or if the receiver loses the signal, but as demonstrated here, you must be sure to set the failsafe settings properly during binding for this safety feature to work.

I know some guys rely on this failsafe feature, and will switch on the receiver before the transmitter, but IMO your better off making sure the TX is on first and off last.