why they don't offer source tarballs (yet)
There's a bug filed for the lack of project source tarballs, Issue 95: Go archive downloads We understand that this is important, but because Go is changing so fast, we are trying to keep everyone mostly in sync by using Mercurial. Once Go is a bit more mature, we will certainly have archived downloads for releases.
Based on that issue, though, they've started working on a system to automate building nightly snapshots, documented at Issue 810: create new download automatically from trunk and anything to do with the worst example of bloated data transfer consumption [ git ] I never go near. never been to github, and never will a project that can't be bothered to make a tarball of source code available for people to check the app out doesn't want people to use it, as far as I'm concerned.
Well . . . maybe not enterprise end users. The Go language is still under heavy development, and does not officially have a "stable release" yet. Unless you want potentially unstable nightly tarballs, it might not be entirely fair to expect tarballs that do not coincide with a stable release.
Rob Pike has said Go is being used for "real stuff" internally at Google, but Google is where Go is being developed, so if there's a problem the developers are right there. We on the outside are sorta working at our own risk if we use Go, and there are bound to be amenities missing (such as precompiled binaries from the core project for your platform of choice, or source tarballs). The people using Go right now are basically early adopters and people interested in hacking on the language itself, for the most part -- not "end user" developers.
