Very true. I have to confess to a very leading question there, as I am building exactly this and thinking long and hard about monetisation. I do like the cable analogy and think it's very true.

I think ads can be done better/more ethically than currently as well though - whether that be less of them, less "native" so they don't appear exactly like posts from your family/friends and with less granular targeting - whether advertisers would go for it is another matter entirely though...