Jim Macklin wrote:

You file a flight plan by telephone, or perhaps a computer
on the Internet. Nobody really knows what name is on the
flight plan and if that person is legal and who is claimed.
Only after an accident or other investigation is the actual
identity of the people on the airplane established.

If your passengers know your name and they want to use your
name and certificate, there is nothing but their ethics to
stop them. If you are a pilot riding as a passenger and
want to be sure, make a call to FSS/ATC before the flight
departs and state that you are NOT the PIC and you did not
file the flight plan. ATC might not have the full details
of the flight plan, such as the name of the pilot. But if
you care, make it a FACT.

One doesn't have to be instrument rated to file an IFR flight plan, do
they? What about a pilot that is working toward their instrument rating?
Their CFII doesn't file the flight plan *for* them, filing is all part
of the training, no?