It's also smack dab in the middle of the East Coast megalopolis, but I get the impression that supply-chain logistics are being handled at a different level.

Regarding the talent pool, as someone who works in the Philly area, I agree it has a lot of well regarded engineering schools nearby, but tech talent doesn't necessarily stay here in the quantities Amazon might find compelling.

Granted, it's a chicken-and-egg issue. The top talent tends to go where the top jobs are, and if the top jobs are in Philly, the top talent might be more inclined to stay.