Asserting p(GOOG goes up over the next year) > 0.9 doesn't seem that absurd to me. Asserting p(GOOG goes up tomorrow) > 0.9 does seem a bit absurd to me.

I'm not sure whether one is ACTUALLY more absurd than the other, but it intuitive FEELS to me that an economist OUGHT to be able to make long-term predictions about major, stable stocks with 90%+ confidence.

Even if this intuition is wrong (and I'd love to hear if it is!), I think many people will share this intuitive reaction. The goal is after all to select an example which is both factually correct AND intuitively appealing to people. So, an unintuitive but true statement would lack that "gut reaction" value.