And TV was the tool before that, and Radio was the tool before that. What's your point?
1. Much more precise user targeting
2. Direct feedback on effectiveness (did the user click-through or even just linger looking at the content?)
TV and radio seem like very crude tools in comparison.
If FB is an industry on the level of TV or radio, then it's almost certainly not overvalued.
The implications and consequences of the consolidation of this power and influence into one company is a different discussion entirely (and an important one).