You need one person responsible for oversight, implementation, maintenance and management of your network security, desktop security, device security and employee security practices.
Obviously, if your company's big enough, the CSO will need a staff -- otherwise he or she'll need plenty of energy, especially if, as is necessary at many small and midsize businesses, the CS0 also continues to carry other business responsibilities.
They'll need plenty of support from management -- one of the largest challenges they'll face is reigning in employee habits, employee devices, employee digital indulgences, even as the external threat environment grows daily (and some days hourly) more dangerous.
But above all, when the designated security officer is selected (or hired) the title must be accompanied by the authority and the ability to enact and enforce sensible, consistent policies and practices throughout your company.
They need, in other words, to be in charge. In this environment, they have to be.