My guess is that Dave Cheney is measuring the cmd/go that comes with the release, meaning it's a different program each time it is measured. Someone probably snuck some new features into it between releases. :-) Like all the -buildmode support for shared libraries, building .so files to load from C programs, etc.

I have been using it in my binary size measurements as I work on http://golang.org/issue/6853, and it has shrunk reasonably well since the 1.6 release. More to come!