In Vegas, yes and no.. on the internet, i doubt a single better could sway a line, unless they were betting a LOT
the line does move, but its a collective effort
.. back to vegas.. some casinos make their own book.. The hard rock, imperial palace, monte carlo, Venetian, etc. Some use a centralized line coming from offshore. If they make thier own book, then as little as 1K can move the line. I used to hate being behind RB when we used to bet the playoffs, as he would bet one side heavy, costing me a half a point or so
. If they use a centralized book for their lines, it is much harder for a single person to move the line, and hence the line will be "truer", meaning some dolt cant come in and put a bunch of money on his alma matre and make the point spread ridiculous, as they could in small books. There are also Max bets per game, half, quarter, prop, etc, all to work to the advantage to the house, just like table limits work to the advantage of the house at table games.
The track obviously makes its own book..I don;t bet horses, but i believe it is completely paramutual and the odds change constantly, as you can watch the odds move by the minute as the money comes in on this horse or that. same with poker, the money the house makes is the rake. everything else is the players money, Bingo as well. That is why poker, bingo and horse and dog tracks are legal in states where casinos and sports betting arent.
As it stands there is only one state in the union where sports betting is legal, and that is Nevada, and there is only one restriction there.. no betting on collegiate athletics that take place in the state of Nevada (obviously to prevent tampering, shaving, or other practices)
The whole point of the Point Spread or Odds is to spread out the money towards an equilibrium, so the risk to the house is minimal, i.e if one team wins, they dont lose a shitload of money. Ideally a book wants a 50-50 split of the money between two teams, and they make the money off the 10% vig they take off the top.