Put yourself in his/her shoes... you have one of the biggest treasures in the world and you invented the technology that can disrupt HUGE organizations.

Will you touch those coins?

I know I will not, until I can find a way to MIX it, in a way that will not be traceable. {None of the methods today, gives total anonymity}

I still think, he/she lost the private key, and are scared that the world would find out. {You would really look like a fool, if you lost 1M bitcoins}

It can happen to anyone.. just ask the guy, who dumped all that coins with his old Harddrive.

Those coins was worth much less, when he got that... so he/she might have not worried too much about securing it.  

Who knows what really happened? If he/she died, how are we to know? Also, how can we differ a normal address from Satoshi's? An address with some early transactions could be a possibility, but the fact remains that he/she could not be alone in mining during those times. He/she could've had his/her friends know about bitcoin back in the days and those people could've mined some coins out of curiosity or help for their friend. There are A LOT of possibilities and probabilities as to what really happened to Satoshi. The only way we can be sure of who he/she is is that someone would stand in the hot seat, prove that he/she is in fact the genius behind bitcoin then problem solved (well it isn't really a problem in the first place).