I think what he means is that you can sell pet food as easily as you can sell books from a given bit of square footage in a server farm.
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I saw a proposal once for special connection-only airports to be built way out in the middle of nowhere so that they wouldn't bother the people in the population centers, and the real estate was cheap (the new Denver airport is almost like this). Telemarketing is sorta like that (Omaha and Sioux City; whoda thunk it?).
I hope server farms are next.
/jordan