LSAM and an unmanned CEV in lunar orbit?

Quoting from http://www.spaceref.com/news/viewnews.html?id=1057 :

"Along with a CEV that carried the flight crew and their support
equipment and propulsion system package, a Lunar Surface Access Module
(LSAM) which was designed to undock from the CEV and take the entire
crew to land upon the moon's surface. Upon completion of the mission,
part of the LSAM would launch off the surface and rendezvous and dock
with the CEV, orbiting unmanned following departure of the flight crew
to the surface. The CEV and LSAM would use a similar approach to the
Apollo CSM/Lunar Module/S-IVB complex to get to and from the moon."

Questions:

What are the risks of having an unpiloted CEV in orbit, rather than
leaving a pilot onboard while the LSAM lands?

How have these risks changed since the days of manned lunar CSMs? Is it
just better automation available? Was having a CMP onboard just a
"consolation prize" in case the LM didn't make it back for a LOR?

How do four astronauts on the Moon make it a "better" mission than
three astronauts on the Moon? It sounds like a lot of ballast (both in
body mass and support materiel) to land and re-launch.