I was lucky enough to listen to Souders talk at Fluent this past week. He talked about Front-end SPOFs and specifically an experience in Beijing where Business Insider didn't load because of a third party widget (Twitter, in his case) being blocked.

One site he mentioned (and great for testing) was webpagetest.org.

Here are the slides from the talk: http://stevesouders.com/talks.php

He blogged about the issue here: http://www.stevesouders.com/blog/2012/03/28/frontend-spof-in...