in-group out-group dynamics. notice how everyone refers to a sports team as "our" team. As if the people watching have anything to do with the team's success.

Yes.

[Though perversely they do influence the success of 'their' team. Where do you think the money comes from?]

Maybe it's a mirror neuron thing?

Assuming the mirror neuron theory is true (I only read the NY Times version), we actually feel a little bit like we are scoring a touchdown when we watch someone else score a touchdown as a spectator. This is even more true if you have played a little bit of football.

Watching an intellectual sitting there thinking deep thoughts, you are mirroring, what? Since you can't observe what is in his head, how can you get any kind of thrill of vicarious participation?

The super model case is more complex. I remember another NY Times article about a study in which women got equally excited seeing beautiful, scantily clad women as seeing good looking, scantily clad men. The hypothesized reason was that the women were putting themselves in the place of those women, their mirror neurons imagining being desired/desirable as those women were, perhaps.

I'm guessing if the super model comes on the screen while the boyfriend/husband/other men are in the room, then it is more a sense that the image on the screen is a rival for attention? Or maybe a little of both.

I don't understand why. I'm of the same slight build as a supermodel, but most people aren't and a beutiful "plus size" model will still make them feel ugly. Though at least it would give more girls a reasonable weight goal.