Value of a broadcast network is proportional to the number of viewers.
Sarnoff's linear law fits broadcast, where value scales with audience. Metcalfe's square and Reed's exponential describe interactive networks, and the three together map the range of network types.
In practice
- A station with a million listeners is worth roughly twice one with half a million, and none of the listeners ever meet.
- A one-way newsletter is worth its subscriber count; a discussion forum is not, which is why the same growth figures mean different things for each.