One of the selling points of Apple's iOS for developers is that the majority of users quickly update to the latest version. However, it seems that Mac owners aren't quite as quick to do so, especially in business environments.
According to Sophos (which offers our favourite security software to Mac), while 55 per cent of home users running its software have updated to Mavericks, just 18 per cent of enterprise users have done so.
It's not unusual for business sites to take a more measured approach to upgrading systems (and Apple's lack of a formal release cycle for updates and upgrades makes planning those updates difficult). The complication is that Apple appears to have stopped issuing major security upgrades for pre-Mavericks releases, which means that those older systems are more vulnerable to exploits.
The lesson? If there are Macs in your work environment, updating them to Mavericks is a crucial security step.
82% of enterprise Mac users not getting security updates [Naked Security]