[aualin]

They have open sourced the tools for this: https://code.google.com/p/closure-stylesheets/#Renaming

The stated reason is to reduce file size.

[Tangaroa]

I would imagine that http gzip compression would cut transmission size just as well regardless of whether the file text is minified or not.

And I would be wrong; this guy found that gzipped minified text can be 50% smaller than the original gzipped file: http://stackoverflow.com/questions/807119/gzip-versus-minify