"...warn your friends"  ... and thank your lawyer.  Why do you think
insurance companies do this?

I am in California.  I just got the renewal bill for my personal
umbrella policy, and the "Important Notice" brochure that always comes
with it said, "The definition of insured is revised so that a person or
organization using an insured's auto, RV or watercraft is no longer
covered."  So, when I let a valet park my car, he's not covered.  If I
loan my car to a friend, relative, or neighbor, they're not covered.  If
my ski boat was running - it isn't right now - and I let a friend drive
it to tow me, he's not covered.  (Yes, I know that my "underlying" car
insurance covers them up to the limits of that policy, but those limits
are only enough to pay for a stubbed toe.)

I called my agent and she was totally unaware of the change, and asked
me to fax her a copy of the brochure.  Then, once she called the
underwriters, she still seemed unconcerned.  She was happy to quote me
the increase in premiums to bring each of my car polcies up to the same
limits that were formerly covered by the Umbrella.  An additional $206
per year.  I will pay the money, because I own a home and it is vital
that I remain insured up to a high limit.

I have taken the trouble to write this post because I think that a lot
of other people will fail to read the "Important Notice" (the brochure
is 17 pages long), will simply write the check like they do every other
year, and will end up with a big gap in their coverage.  And their
insurance agent won't take the trouble to call them or write them a
personal letter telling about the big gap that just opened up in their
coverage.  So, look out!   And warn your friends.

Ham