To this end we work with numerous third-party hosts to help them update their customers, and have invested significantly in a notification and upgrade system for 10k+ plugins, 1k+ themes, and of course the core software. This was a particular PITA because runs on so many platforms with wildly different constraints and configurations. We blog, tweet, and email 200k people whenever there's a new release and offer free help on our forums to anyone who is stuck. Someday we might even offer auto-update in core just like many hosts already do.
My comment was more aimed at the HN audience which might want pro tips for staying updated or more defense in depth. For example I have a cron job run `svn up` on my site every morning which keeps it up to date whether I'm in front of my computer or on a beach sipping mai tais.