http://well.blogs.nytimes.com/2009/0...l-exercise/?em

Most interesting to me:

Q Should we keep sipping fluids while we’re exercising?

Answer

How we drink can make a difference in how optimally we hydrate our body. A lot of people sip liquids, but gulping is better. Gulps of fluid leave the stomach more rapidly. It’s important to do this. It seems counterintuitive, it seems like gulping would cause a cramp. People are more likely to have stomach cramps sipping because fluid stays in their gut too long.

When you take more fluid in, gulps as opposed to sips, you have a greater volume of fluid in the stomach. That stimulates the activity of the stretch receptors in the stomach, which then increase intra-gastric pressure and promote faster emptying. This is why gulping is preferred.
It's difficult for me to take more than a few ounces at a time while running (since I can't breathe and drink at the same time). But I've already been trying to train myself to drink larger amounts less frequently, so I'll be able to rely on aid stations during longer events. It's good to know that there's science behind it.