QUOTE(existwhere? @ Nov 26 2007, 01:39 AM)

Where? (serious answer please)
They've come to recruit at my University a lot, and they explained a little of that, but not at a very technical level. But essentially they
DON'T go in for huge storage servers - they just run so many commodity desktops that the couple hundred gig on each one adds up to something massive. They are very evasive on numbers, but Wikipedia suggests that they have ~450,000 servers, and that number is probably wrong but also probably within the correct order of magnitude. Then they run this massive specialized file system over all the machines that makes them one big honking logical drive.
Again, very high level - they absolutely refused to go into more detail.