Since the infamous "GoogleGuy" joined the WebmasterWorld forums in early 2000, the man behind the name has always been a mystery of some sorts.
For the first time in history, we have official confirmation in way of a written book. A book that has 100% validity behind it, In The Plex by Steven Levy. In fact, it is one of the few Google books I have ever purchased - I normally get books on Google for free.
Conduct a Google Book search for In The Plex Google Guy and bam, here you go:
The book reads:
Using the pseudonym "Google Guy," Cutts would answer questions and try as best he could to dispel various conspiracy theories, many of them centered around the suspicion that a sure way to rise in search rankings was to buy ads from...
So there we have it, first time Google Guy outed in a print book.
Forum discussion at Google Blogoscoped Forums.