That's the inherit design problem with Bitcoin. There's only a limited amount at the moment and rather Satoshi change his mind and up the limit in order to replace these lost coins is too much of an unknown to account for.

Again, this is why Bitcoin is alot like gold. Because there is gold out there that is "lost" forever when people stashed them in unknown location or bury them with dead bodies. We can are only making educated assumptions based on some what realistic estimate. That's the problem with putting a hard value on any assets or companies - some of the assumptions you make can change rather quickly due to the operating and business environment.

But by doing this exercise give me a good idea what Bitcoin can potentially worth one day given the world isn't trying to shut it down like they are trying in China. It's better than randomly say "hey bitcoin is worth $400 billions and 40,000 per coin!"

I assume the Winklevoss hire an analyst or two to do the dirty work and hopefully they won't steal their work this time around.