I've been looking around for some more detailed information about the "Site Reliability Engineering" positions at Google. Apparently the role is a real mix of very large-scale system administration, planning and automation.
I've collected some links to public info about the job.
The Google channel has a promotional video from one engineer about the role - he tells a quick story about being on call to monitor and address problems with Google talk.
A set of slides from a talk by James Youngman at the UK Unix & Open Systems User's Group gives a good description of the general task, and dives deeper into two specific examples - powering down failed disks, and protecting data with checksums, exploring how straightforward ideas can explode at scale. (These slides also have potentially the best proprietary-information disclaimer I've ever seen: "This has been written entirely in ASCII. No EBCDIC or animal fat.")
Here is another set of slides with a quick overview, from a 'lightning talk'.
A sampling of what Google SRE engineers put in their public resumes about their job includes quite a span - from troubleshooting mission critical services to writing automation software (in Python).
And finally, an interesting post from 2006 about the theory behind Google's hiring strategy, summarized as "only hire candidates who are above the mean of your current employees".