Good question - here's the answer http://bitcoinreport.blogspot.com/2011/01/first-bitcoins-ever-spent.html
Thank you for satisfying my curiosity. I think it's almost certain that such an early block would have been generated by Satoshi. Of course, "spent" is quite a strong term. The coins might just have been sent to a different wallet.
It was an IP-address based payment.You might find this new post interesting : http://bitcoinreport.blogspot.com/2011/01/life-of-bitcoin.html
I've analysed all of the transactions stemming from that first transfer and produced a graph showing how the bitcoins got spread around and passed between different addresses.
