Yes indeedy. That is the key. Mine are the first my mechanic has ever seen
that wore out strictly from metal fatigue, and not dirt/water ingress due
to split boots.

Anyway, I got pics yesterday!
http://www.tegger.com/hondafaq/misc/worn_cv-joint/

What has happened here is that two of the six balls had failed from metal
fatigue. These balls are about 3/4" in diameter, and carry all the load
transmitted by the joints. The hardened outer layer had spalled off in
pieces into the races. Those pieces had then damaged the races by being
pressed into them as the joint turned and rotated. Most of the damage was
done to the inner race. Only one spot was found on the outer race, that
pointed out by the yellow arrow.

Now that I've had time to consider this, the noise started over a year ago,
but I couldn't pinpoint where it was coming from. It appeared to be random
for the longest time, becoming more consistent only very recently, and
becoming quite loud only in the last couple of weeks.

I would say the joint began making noise at about 240,000 miles, so I've
been driving with a worn outer joint for 25,000 miles.

---------

Ultimately, it turns out my car had three layers of problems, none of which
were particularly serious in themselves, but when taken together
substantially reduced driving enjoyment. When one layer was removed, it
exposed the other.

1) Badly mounted tires causing vibration at speed. The poor mounting job
was obvious when tires were spun by hand and observed. My guy fixed that,
and that vibration was gone, but another surfaced...

2) Worn CV joints. The inners were causing a vibration on acceleration, as
well as steering wheel wobble on acceleration from a standstill. The
driver's side outer's balls were spalling from metal fatigue, and were
clunking badly through tight right turns. Replacement of the shafts fixed
that, but now a third vibration was evident, this one *much* less intense
than the others...

3) Possible injector problem. My mechanic suspects that the injectors are
worn to the point that they are not all metering the exact same amount of
fuel with each pulse. Ordinarily, this is not noticeable, but similarly to
tires or the exhaust system, a vibration manifests at a specific resonance
point in the engine's operating range. That spot is around 3,500-4,000 RPM.
When you lift off the pedal, the injectors shut off and the vibration goes
away. When you press on the pedal again, the injectors turn on, and the
vibration reappears. It's very slight, and feels more like harshness rather
than a vibration.

The third item is still subject to confirmation, but the engine mounts have
been ruled out, as have compression and ignition variance between
combustion chambers.

That third item may also account for two other things that have recently
arisen:
1) A slightly elevated CO reading at the last emissions test, indicating
excess mixture richness.
2) Fuel dilution of the engine's oil, as found in an oil analysis I just
had done. This dilution has resulted in slightly elevated piston wear.
3) Gas mileage is still around 28mpg, where it's been for years, so either
this problem has been around for a long time, or it's small enough that
it's not affecting mileage.

New injectors are almost $300 each, so some more research will have to be
done here.

Stay tuned...