There are consistent "great numbers" at the beach I frequent in Southeastern
Broward County.  For example, this weekend I picked up about 50 large,
freshly dead ones, and 20 immature specimens just beach walking.  The summer
before last, my friend and I found about 1,000 in one weekend snorkeling just
offshore!  However, in the period of winter/1998 to summer/1999, olives, and
shells of any kind, were extremely scarce.  I think this was due to the
hurricane that came through the Keys - because that's the first prolonged
"dry spell" ever on that beach (confirmed by all the old-timers who trod the
shores!).
Happy holidays and to those who can make it, see ya on the beach!!!
Joni