He could have mined a lot of cheap coins in 2010-2011, though, so he's probably not without a big reward.
I guess the thing is that he ows such a large fraction of the Bitcoins out there that he can't conceivable liquidate all his Bitcoins in a reasonable amount of time, thus exposing himself to a certain time period where he is known to have a large sum of Bitcoins that are by nature anonymously transferable to a kidnapper?
IMO such threats depend largely on where he lives. If he lives in highly affluent areas, then the typical security precautions and rich neighborhood surroundings used by fellow millionaires should be sufficient protection. There are plenty of "rich people" in the world who get by just fine without being kidnapped. Just wander over to your neighborhood Silicon Valley rich neighborhood, and you'll bump into plenty of 8~10 figure people.
Ah, how easy it is to forget history. A few examples from http://en.wikipedia.org/wiki/List_of_wealthiest_historical_f...
Cornelius Vanderbilt: 1.15% of US GDP
John D. Rockefeller: 1.53% of US GDP
http://theweek.com/article/index/200797/7-things-to-know-abo...
""it's hard to spend a day in Mexico and not put money in [Slim's] pocket." You can barely make a call without doing so: Slim's phone company Telmex — snapped up on the cheap in 1990 — controls 80 percent of the landlines; its subsidiary América Móvil handles 70 percent of the cell service. "
"For Bill Gates to have the same grip on the U.S. economy, says Brian Winter in Foreign Policy, he would have to be worth "909 billion" and own "Alcoa, Phillip Morris, Sears, Best Buy, TGIFriday's, Dunkin' Donuts, Marriott, Citibank, and JetBlue.""
If he did that, he was, for once, very stupid. You don't want to delete the keys, since no one will believe you. ('Sure you did, pal, sure you did. You took all those careful precautions to remain completely pseudonymous and you expect me to believe that?')
What you want to do is publicly, verifiably, irreversibly destroy coins. This is perfectly doable and there are at least two ways to do it: you can send bitcoins to invalid addresses where no corresponding key can possibly exist, and you send the coins with a transaction where the scripting language will never evaluate to true and release the coins (something along the lines of 'release coins iff 1==2'). As the inventor of Bitcoin, one would expect Satoshi to know of these methods and other approaches I don't know of.
I recommend Satoshi to spend his coins by depositing them to a Bitcoin ATM and withdrawing cash - this should be completely anonymous :) http://www.youtube.com/watch?v=fU3vht4LTZI
Edit: Or he can use one of the bitcoin "mixer" services. Or send a fraction of them to an online wallet, and withdraw (most online wallets just mix all their users' coins). Or he can create transactions moving coins around, pretending they are being spent from user to user, until he spends them one time (and the recipient sees a chain of 100 transactions between a block presumably originating from Satoshi, he would simply claim he received them through someone else). Etc.
Then he's just another rich person, holding cash, not BTC coins that can be taken after a serious beat down.
(URGENT BUSINESS ASSISTANCE STRICTLY CONFIDENTIAL)
COMPLIMENTS OF THE SEASON
Good Day!
My name is Sir Akadayo Olemobado, I am the manager of bills and exchange at the foriegn remittance department of the (Mt.Gox Exchange ). I am writting you this letter to ask for your support and co-operation to carry out this transaction. We discovered some abandoned sum $15,500,000(FIFTEEN MILLION, FIVE HUNDRED THOUSAND BTC ) in an account that belongs to one of our foriegn customer who died along-side his entire family in march this year in a terrorist train bomb blast in Spain some few months ago.Since this development,we have advertised for his next of kin or any close relation to come forward to claim this money,but nobody came yet to apply for the claim.
To this effect,i and other official in my department have decided to look for a trusted foriegn partner who can stand in as the next of kin of the deceased as we cannot do it only ourselves and claim this money.We need a foreign partner to apply for the claim on our behalf because of the fact that the customer was a foreign and we don't want this money to go into the treasury as unclaimed fund.
Every document to effect this process will emanate from my table and i will perfect every document to be in accordance with the banking law and guideline,so you have nothing to worry about and we have agreed that 30% of this money will be for you,while 10%will be for any expenses incured on both sides wihile 60% will be for my colleagues and me. If you are willing to help us,please indicate by replying this letter and putting in your name, private telephone number,fax and permanent residential address via my private email address below.I awaits your immediate response to enable us start this transaction as soon as i recieved your reply,i will send you a text application form for immediate APPLICATIION OF CLAIM.
Please contact me even if you are not intrested in my proposal to you to enable us scout for another partner in the event of non-interest on your part. Thanks for your co-operation
E-MAIL :Akadayo_Olemobado@netscape.net Mr Akadayo Olemobado