profmonocle

As a software engineer, I can tell you it might add somewhat to the initial development cost, but it adds nothing to the per-device cost.

1) we were issuing IPv4 space in 2010 and more than 10 /8's per year, so recovering another handful doesn't change IPv4's outlook in the least

I always point to this graph by Geoff Huston to drive this point home: http://www.potaroo.net/tools/ipv4/fig25.png Not sure how much legacy space people think is out there, but it wouldn't be nearly enough in any case. (Same goes for trying to use the 240/4 space.)

Better to focus on IPv6 deployment than trying to squeeze more blood from the IPv4 stone.

Or is the policy "Once allocated, never questioned"?

That's not the policy now, but it was basically the policy when that space was assigned, and they're grandfathered in. The legacy space is basically untouchable unless the owners decide to sell it or return it.

Although this was completely voluntary, right? My understanding is there's no way for ARIN to force legacy v4 space holders to return blocks, which is what I think enitlas was asking.

If you don't use IP addresses on a regular basis, you really don't need to care at all. The way you use the Internet won't change. Certain services may be degraded if they don't eventually support IPv6, but that's their responsibility to deal with.