Testing from within their own datacenters would be biased _very_ heavily toward their own service, don't you think? These tests are only meaningful if performed on an external ISP. Note also that if you do the test it says "US East (Virginia) - IE 8 - DSL", suggesting that it's on a regular DSL connection, not a EC2 box.

WebPageTest originally came out of AOL as an open source project. Patrick Meenan was the lead on that. He recently took a job at Google, but WebPageTest is still open source and has contributions from lots of companies who care about performance. For example, my company Torbit sponsors a WebPageTest instance in Ireland.

AWS regions and what Google is using are common to many service providers. These are typical peering locations. Google does have the benefit of having caches local to various ISPs.

That doesn't prove much though, does it? "Northern Virginia" is a pretty broad region.

Weird that their default test browser is IE8 too. Hello Chrome ?

A dead link by Canopy below says:

"WebPagetest is not run by Google."

and points to their about page. Apparently, he's right.