It turns out that he's a fraud. The proof he supplied is not valid. He claimed that the message he has signed was created by the same key used to sign a message Satoshi once posted before. But actually it's a transaction hash from 2009 of a bitcoin transfer.
Essentially he confused the BBC with techno-babble making them believe that a satoshi transaction hash was a message signature. What he did is something anyone could do due to the bitcoin blockchain making all transactions public. He's just a trickster and this is the second time he has tried to deceive the world into believing he is the creator of Bitcoin.
The last time that he tried this he sent out two pieces of evidence, one to Gawker and one to some other news site and it was like a fake leak of information naming him as Satoshi and it was involving some Australian tax thing.
For some reason this guy is really hard up for people to believe he's Satoshi but people in the bitcoin community (I'm not in that group myself) are all adamant he is a fraud and they've provided detailed proofs that show his evidence is a load of made up rubbish.
Quite sad as I wanted to believe the real Satoshi had come forward finally but I guess we're still some ways away from that. By the way he also claimed all his early bitcoins (worth about 445 million or so dollars) are held in a "trust" until 2020. Guys smoking something that's for sure.