I would say that the CEO's key role is more to make sure that key constituencies and stakeholders are addressed as effectively as possible, not necessarily to address them directly themselves. Sometimes it is actually more effective to delegate that job. Having said that, it certainly seems to be the case that the closer a constituency is to the core competency of the business, the more likely it is that they should be addressed directly by the CEO, and I buy the argument that moderators and heavy contributors should be the core competency or reddit.