+Roger, as I'm curious as to the rationale.

On Tue, Mar 18, 2014 at 9:12 PM, grarpamp <grarpamp@gmail.com> wrote:
> If I'm not mistaken, you need to open two of the ports 80, 443 and 6667
> to gain the Exit flag

It's in dir-spec.txt as such. Probably under some rationale of
making nodes most widely beneficial. I'd think soaking up btc
traffic would be useful, if exit traffic stats supported that
need... is it 20GB per thick btc client now?, plus ongoing...

Yes, and allowing people to exit only Bitcoin traffic seems beneficial in other ways:  you're not likely to get abuse reports from just allowing port 8333, so the cost of being an exit for that is much lower. And it'd indeed take bandwidth pressure off other nodes.
 
> but not having that flag doesn't mean that you're not
> an exit
> Try waiting some days to see if there's some traffic on port 8333.

The atlas graphs do show traffic for such nodes
providing essentially just 8333. They're usable manually,
just not automagically by the client I think. I forget
how their traffic is picked up.

The globe page for my node shows "exit probability: 0" so I guess I'm indeed not being sent any.
 
There are 850+ nodes allowing 8333.

Have you considered running an onion:8333 seed node
to both serve btcnet and keep traffic off the exits?

Yes but it doesn't get any traffic for reasons I haven't bothered to figure out yet. Anyway we can't run all of Bitcoin over Tor because it'd kill off our (admittedly quite weak) anti-sybil defences.