There has been much speculation on the subject, you could have chosen from a lot of decent articles like this:
I'd rather read posts from above-top-secret than the bitcoin forums.
"Satoshi definitely saw this as a strike against the malignant forces that national fiat currencies and the parasitic monetary/finance system has become.
Enslaving us all in unpayable debts and endless taxation for wars and bankster bonuses ... it is now a criminal system that will go down in history and those at top aren't doing squat to change it, except personal enrichment. (Oh but we are chasing bad guys playing poker online, trading goldbits and smoking weed on their couches ... whatta a load of BS)."
-- I think that pretty much sums it up ... likely one or more people who wanted to remain anonymous.
The "problem" with Bitcoin right now is that much of its new value is based on rumors and hype. But it's base value (say that of ~$15 or so) is pretty real, as real as it can be. But most or all of the difference between $15 and its current price of $25 or whatever it is now, seems to have been made mostly on hype, and I hope it ends soon. And this is only happening right now because the transaction value is still pretty tiny of around $200 million or so. Get that to $200 billion or $2 trillion, and then this shouldn't happen as often or with as much variability.
I have read this PDF before, a while ago, and I don't remember that stat. A quick glance tells me that they say that 2 addresses have over 500,000 Bitcoins, but that's just 4.6% (or more, obviously) of the total 10.7M issued so far. And there's no proof that this is the creator of Bitcoin. In fact, it's more likely one of the large exchanges!
So, please help me understand your statement. If it's buried in the text of that PDF, my apologies.
The implication is that some early adopters (possibly the creators) have stockpiled bitcoins in that entity.