For more discussion on this topic, please refer to these discussion threads: https://groups.google.com/forum/#!topic/spdy-dev/_uvxTJkeCP0 https://groups.google.com/forum/#!topic/spdy-dev/XDudMZSq3e4
And note that your reference is slightly misleading (I don't think you intended this). It's true, the vast majority of hosts supporting SPDY are running nginx. In practice though, the vast majority of these hosts are Cloudflare or WordPress.com hosted sites. Both run newer versions of nginx with SPDY/3.1 support.