Thanks for the assist folks.  Based on what you all said I tracked down that
update-manager had offered, and I permited, an update to libgphoto2 which on
installation updated /etc/udev/rules.d/45-libgphoto2.rules (the only file in
that directory which has changed recently).  The beginning of that file
looks like:

# udev rules file for libgphoto2 devices (udev >= 0.98)
#
SUBSYSTEM!="usb*", GOTO="libgphoto2_rules_end"
ACTION!="add", GOTO="libgphoto2_rules_end"

ATTRS{idVendor}=="0553", ATTRS{idProduct}=="0202", MODE="0660",
GROUP="plugdev"
ATTRS{idVendor}=="06bd", ATTRS{idProduct}=="0403", MODE="0660",
GROUP="plugdev"
ATTRS{idVendor}=="06bd", ATTRS{idProduct}=="0404", MODE="0660",
GROUP="plugdev"
ATTRS{idVendor}=="04fc", ATTRS{idProduct}=="504b", MODE="0660",
GROUP="plugdev"

and goes on with lots of those lines.  I seem to recall being required to
restart the system because of something in the group of updates.  Perhaps it
was this update since this file might need to be reread by a driver module
loaded to (or in) the kernel.  As I initially reported I saw the lines on
startup (restart?) because I have the quiet splash turned off.  After seeing
them is why I checked the log.

Anyway, my strong suspicion now is that the log lines I was questioning are
either generic reports of adding unspecified products to the list, or error
reports of products not being added because the vendor (and therefore
product) were not recognized (poor reporting IMHO).  I hope the former, but
fear the latter (solely based on the messages appearing in syslog).

It would be good to know how to find out which is the case, but I am no
longer worried about it.

<snip>
-- 
Be who you are and say what you feel, because those who mind don't matter
and those who matter don't mind.  - Dr. Seuss