Explicit opt-in can even be sent via the renewal notices -- i.e. 90 days before expiry, 60 days, 30 days, etc. The registrant can click a link, fill in information as to where to send any auction proceeds (along with income tax information), and set the ball rolling on an auction that they can not stop (i.e. the auctioneer would control the name from that point forward, and complete the transfer to the new party).
It's the "can not stop" part that scares me: say they had opted in when they registered so their expired name goes to auction, but at renewal time the registrant was unreachable for a long period of time for whatever reason - out of the country, sick, extremely busy, email down, email eaten by spam filters, natural disaster, war, phone disconnected, they summer at the coast/winter in aspen, etc, etc, etc.
The registrant would have had ~60+ days to get their name back after it expired and stopped working under the current system, and assuming they were contacted for 60 days prior to expiration, this is probably enough time to cover the vast majority of situations.
I would consider it an insult to come home or back to work, find out my domain isn't working, try to renew but get told it's gone to auction, then receive a piddly little check for my share of the revenue.
I know many of us (especially others in the drop game) take a dim view of those who can't be bothered to renew prior to expiration, but when you're the aloof registrant who just expects things to work (or the reseller to the aloof registrant) things look different.
It is essential to consider the needs of the original (primary) customer and hold them above the needs of the secondary customer - even if the secondary customer is willing to pay a significant premium to get you to ignore the primary customer. Doing otherwise would make you (Tucows and/or Reseller) as bad as NSI.
-Russ
