What about the situation where a single pilot aircraft is being operated by a pilot with a view limiting device (ie a hood). The rules require he have a safety pilot (rated in the aircraft). There are now two pilots required by law, so isn't this a multi crew environment? In this case what does the safety pilot log - if anything?
As far as I'm aware the safety pilot is not an active crew member, hence he does not log anything (or rather anything that will add up to his total flight time, you can still log it to keep track of what you did on that day, sort of like a diary) and the operation is still not multicrew as the PIC is still solely responsible for the safe conduct of the flight. The safety pilot's role is only to monitor and point out any issue to the PIC so that he can stop the exercise should it become unsafe to continue.
I'm assuming you're not referring to actual training and the second pilot is not a certified flight instructor.
Ciao,
Dg800