While momentum might play into it in a small way, it's not nearly as much as fans believe or remember (and I'm sure that
@fluoxetine is coming at it from a gambling angle like I am, where you track these things to be able to make in-game plays, and realize how much it's overblown to most when you look at the real numbers). It's like the arguments that people have when they mock the analytics of NFL coaches going for 2 when down 9 or down 8...even though the math backs it up, I always hear "but you lose the momentum". In those spots, the math is so strong that momentum shouldn't be a factor in your decision.
It's like Home field/court advantage...manual casual fans greatly over-exaggerate it's impact. A fan on the PSU site claimed that if we played all of our home games at Rec Hall instead of the BJC this year, we'd be undefeated. When I pointed out that we've lost games by 9, 9, 8, and 4 at home, he countered that Rec Hall is worth 10 more points than the BJC. In actuality, that number is probably closer to something between 0 and 1 point. (and those that don't handicap/model seriously do the same thing with injuries, overestimating their impact)