A couple of big names — Marissa Mayer (Google), Matt Mullenweg (Wordpress), Eric Schurman (Bing), Jake Brutlag (Google), etc. — talking and showing data about the influence of site performance on users behavior.
Eric Schurman and Jake Brutlag: Performance Related Changes and their User Impact
Marissa Mayer: In Search of… A better, faster, stronger Web
Philip Dixon: Shopzilla’s Site Redo - You Get What You Measure
David Wei and Changhao Jiang: Frontend Performance Engineering in Facebook
Kyle Scholz and Yaron Friedman: High Performance Search at Google
Matt Mullenweg: Improving Performance in Mature Web Apps
