But I didn't say that eyeball-hours have a fixed value. I said that there is a fixed supply (at a point in time).
It is necessary to get the eyeball-hours in the first place. That Facebook may be able to wring more out of them than Google is important; but from Google's POV the attrition of its eyeball-hour supply is more important.
Eyeballs aren't necessary, if you accept that automated consultative selling is possible (unproven so far!). The model stops being advertisement-riding-on-content, and instead is a message sent directly to you (or that you request).
Well, I guess it must be somewhat possible, because overture/goto did it... (they aren't around any more because Yahoo acquired them, and their technique was adopted by Google - but no one else has done it, so maybe it's not workable any more. Perhaps because Google does it (i.e. it's a feature of Google search - just turn off adblock and ignore the search results - and Google has better access to users (eyeballs), so advertisers would prefer it.))
What I'm saying is that it doesn't really need eyeballs, but what eyeballs bring: access to you. There are other ways to gain that access (that aren't as good so far). It does need to know you intimately, so content probably helps (is crucial?). And you need to trust it. (Which you would do, if it turned out really to be fantastically helpful.) It also needs fantastic AI to predict your needs before you do...
My understanding is that getting info about users was the business model behind (the failed) Color. Maybe, in theory, content/eyeballs aren't strictly necessary for automated-consultative-selling, but perhaps it's the only effective way to get the information to model them, and to get access to them, in practice, at the moment.
But I didn't say that eyeball-hours have a fixed value. I said that there is a fixed supply (at a point in time).
It is necessary to get the eyeball-hours in the first place. That Facebook may be able to wring more out of them than Google is important; but from Google's POV the attrition of its eyeball-hour supply is more important.