> We care deeply about keeping SRE an engineering function, so our rule of thumb is that an SRE team must spend at least 50% of its time doing development.

Prior to SRE any good system administrator was doing this: "if it's worth doing, it's worth automating". But there was another half who were cutting and pasting shit from Word files into Solaris boxes. sysadmin -> SRE seems to have cleaned out the chaff.