Finbar wrote:
And unlike flying with an out-of-date chute, when
you turn off a transponder your crime is broadcast to the world (or,
technically, your compliance with the law is no longer broadcast!).

Of course, the nice thing about Mode C (as opposed to Mode S), is that
ATC doesn't know who you are, unless you explicitly identify yourself.

The big transports may be a more impressive threat, but getting
Clobbered by a C-182 or one of the many low-flying
(clearly not on flight following!) GA aircraft I see out there, from
warbirds to Lears (!), could be pretty fatal too. So I'm wondering
about that one.

I can see and avoid GA aircraft ahead of me, and the ones behind aren't
closing on me all that fast, so there's some chance they'll see me in
time. The thing about transports is that at the altitudes I'm flying
they are moving fast relative to me, and either climbing or descending
at a fairly high rate. In my experience, the aircraft I've had near
miss experiences with have been other gliders, airliners, and military
aircraft, in roughly that order of frequency. I see GA aircraft all of
the time, but so far, always at enough distance to avoid.

If the passive proximity warning systems prove to be effective, I'd say
they are a decent alternative, except perhaps in those areas where there
no radar coverage. Since I normally have the transponder off in those
areas, it's not a huge disadvantage. But, I've yet to come across much
objective evidence that convinces me they are effective. Maybe as
Bumper and others use them for a while, I'll be convinced...

Marc