Have you noticed a little problem at parties? You get introduced to groups of people and immediately forget all their names. There's an effect that explains why things like this are such a problem.
Here is a social problem so pervasive that Eddie Izzard has a famous routine about it. You have undoubtedly experienced it. You go to a party, you walk up to a group of people, and you are introduced to them. Even if this were a simple memory test, done in a quiet environment, it would be difficult. It's hard to learn the names of large chunks of people, and you would probably forget one or two names over the course of fifteen minutes. At a party, you forget them all in a moment. You forget them so quickly and completely, that you couldn't have done a better job of forgetting if your life depended on it. Why?
It doesn't just take a good brain to memorize names. It takes time and attention, neither of which you have in that situation. As each person is listed, we are waiting for the next person's name. This provokes what's known as the next-in-line effect.
The next-in-line effect happens when someone is waiting for their turn to speak during an organized event. Researchers tested it by having people in small, circular groups take turns giving out information, then testing them to see which snippets of information they remembered. Each participant's memory was just fine, right up until they got to the information imparted by the person who talked just before they themselves were "up." Suddenly, they remembered nothing. Yes, they were listening when the person before them was talking. They just weren't paying attention. Their mind was already on the next task.
When we see a group of people coming towards us with their hands out for handshakes, we're in a situation in which we know we'll have to take in a cascade of information, and we try to prepare for it. This is exactly the wrong thing to do. We try to simultaneously greet the person in front of us, and get ready for the next person in line. As it turns out, we can either take in and store information, or get ready for the next grouping of information. Since we try to do two things at once, we fail at both.
Of course, I forget people's names when they are introduced to me one by one in quiet areas. I believe that's called the bad-person effect.