For those of you who do not know the real meaning of the point spread, let someone who grew up helping his grandfather sort out sports parlay cards (illegal at the time) fill you in.
The spread has nothing to do with the number of points the oddsmaker feels the favorite will win by. It's set to the number of points the oddsmaker feels will result in the public betting an equal amount of money on each team. Since the bookies make their money on the "vig" (a misnomer for their service charge) - they want to have enough coming in on the loser to cover their payout, after service charges are deducted, on the the winner.
The reason the line changes (or "moves") up until game time is reflective on the amount of money bet on each team up until then. As one team gets a lot of "play", they adjust the odds to make it more attractive to bet on the other team. Remember - the objective is to get an equal amount bet on each team. When the betting is way out of balance, they lay off bets with other bookies to cover the possibility of taking a bath.
If you think bookies lose a lot of money when there is a huge upset (a common misconception), you're wrong.
BTW - the real "vig" (short for "vigorish") is the interest rate a loan shark charges, usually just a liiiiiitle above prime.
