As long as you pick your spots carefully...
for example...there was a point in tonight's Miami/Boston game in which Boston was +8 1/2. It was in the third quarter when Miami was on a run with around a 6 point lead. While Boston was having the first string of flat possessions of the game, it was clear that no team had a commanding control of the game. It only took Boston a couple solid defensive and offensive possessions and they were right back in the game. That is the beauty of live in-game play. The pre-game spreads are usually very sharp, and are virtual coinflips. While you can certainly pick your shots with pre-game spreads, it seems as though you can find better opportunities with live spreads. Good cappers can gauge if a team seems to be pulling away, or are just on a temporary cold streak.