SPDY is protocol created by Google to overcome the problems of HTTP/1.1 (pipelining) and the absence of HTTP/2.0, a way to tunnel all traffic through one pipe/socket without additional TCP overhead (handshakes etc). Right now it is supported in modern version of all minus one browsers (http://en.wikipedia.org/wiki/SPDY#Browser_support_and_usage) and it is the base of HTTP/2.0
Even if it was only for chrome/chromium browsers, still a very easy and cheap way to make d.o a lot faster without many if any risks. The downers are, it uses HTTPS so a certificate (we already have that), but this also makes it nearly impossible to troubleshoot from a command line right now. In due time, better tools will come, but right now not many good tools are there. facebook and all 8.google.com services including youtube use SPDY and we should really do this, easy to setup and test and to deploy once the thumbs are up. There are SPDY modules for NGINX and Apache, so enabling this doesn't lock us in on either one of them.
I have done some SPDY implmentations and can help, but really it is a no brainer.