It was pretty simple detective work. It came from this post here on ycombinator.
You can see it was involved in a transaction for 2.2 BTC in July of 2011. 2.2BTC is about right for what he claimed the customer bought: 2 crepes.
Okay, Blockchain detectives, go. Let’s investigate. Everyone thinks this man is Satoshi, so I’m not worried about invading his privacy. If we can show he is or he isn’t, we should. We have a moral imperative. If he isn’t Satoshi, we need to get the word out, and get him to be left alone like he wants. If he is Satoshi, more drastic measures may need to be taken to get him away from harassment, like those suggested on Reddit by Bruce Fenton.