It’s possible that some users may even find that the HTTPS version of a web site is faster than HTTP. This can happen if they sit behind a coporate HTTP proxy that normal intercepts, examines and records web traffic. An HTTPS connection will often just be forwarded as a simple TCP connection through the proxy because HTTPS traffic cannot be intercepted. It’s this bypassing that can lead to improved performance.
Source: http://blog.httpwatch.com/2011/01/28/top-7-myths-about-https/
I can actually confirm this to be true in some cases. Even worse is that people might think that HTTPS prevents corporate from sniffing - that is not always the case 🙂