I think number of unspendable bitcoin is more than this because there are also lots of addresses which contain bitcoins and nobody have access to it, like addresses of wallets whose password were lost, known addresses of satoshi etc. However nice listing...
That's true, but there is no way to confirm that they are really lost, or that the people in question really haven't access to their coins anymore. That's why it's better to wait and not include them into compiled "lost coins" lists. I from time to time spend some hours on analyzing very old wallet addresses containing plenty of coins. In some cases you will see that after 5 or 6 years the person behind one of these addresses starts moving his coins. That's why I never take for granted that they lost access to their wallets.
Yes, it is too early to call an in active bitcoin address as lost because the holder of the private key for that address may be waiting for more time for the bitcoin to appreciate and then cash in some day when they are worth a fortune. Or may be they have forgot about it. Who knows! it will stay as a mystery.