It seems _why is a very enigmatic figure and his real identity seems to be not known. However I respect his desire to stay anonymous despite the fame he deserves for being a very creative and respectable hacker.
I think his real identity is very well known, isn't it? He's why the lucky stiff. (Admittedly my Argentine friends might complain that since we don't know the number of his Documento Nacional de Identidad, we don't really know his identity. It's really hard to explain to notaries and the like that my new US passport came with a new passport number, and that does not mean that I am not the same person.)
His real name was on his Wikipedia entry for a brief period. At the time I confirmed with others that it was true, but then it was removed and hasn't been back since. I've not been able to find it with a casual browse (and I've forgotten it). This is all the more amusing since he wrote the foreword for my book :)
The page history says that his last name might be Malsky.
He might as well be a group of people - sorta like Aristoteles or Homer (the greek one, not the Simpson)!
Me and my friends once tried to uncover his real name, with no success. It seems he has registered all his domains with the name _why the lucky stiff (the WHOIS page said "the lucky stiff, _why")
Maybe that is his real name?
His name is out there, if you really care. If I recall, he's attended at least one conference.