For proof that Silicon Valley is home to an especially clubby concentration of wealth, just take a short walk down a stretch of Palo Alto road. The one where Facebook's young paper billionaire lives next to a young YouTube millionaire.

Or so we hear from a College Terrace tipster claiming to be familiar with the residences of Facebook co-founder Mark Zuckerberg (paper wealth: $2 billion) and YouTube co-founder Jawed Karim (estimated wealth: $64 million). Public records confirm that Karim lives in the two-by-twelve-block Palo Alto neighbohood, adjacent to Stanford University; records indicate Zuckerberg has for months occupied property nearby, albeit in the form of Facebook's new headquarters, a short walk away from Karim.

But Zuckerberg is now a neighbor in a much more real sense, according to our tipster, renting a home right next door to Karim (as in side by side) on the same street. The brief commute would be one good reason for living there. Another: It looks like a leafy, laid back area, according to the ample photographs of the street on Google Maps. Based on Karim's address this is the block they share:

Why are Zuckerberg's neighbors ratting out his address? His employees are taking up the parking, and, we're told, residents complain that the fast-growing company is not providing enough spots (they're apparently not mollified by a proposal to begin requiring residential permits in some areas). You should probably get on that, Mark; these people know where you live.

In the meantime, local residents are missing the real outrage: That, in their 'hood, even insanely wealthy startup founders live in what most American suburbanites would consider modest pads.