I also read something once that resonated, though I can't speak to how accurate it is. The idea is that when people are more introverted or discussing a technical topic, they tend to look away while speaking, then make eye contact to signal that it is the listener's turn to talk. Me staring at my shoes while I concentrate on conveying accurate information, then looking at the listener to see if my words made any sense at all. :-)
When people are more extroverted or on a less technical topic, there is a tendency to make eye contact while speaking, then look away when it is the listeners turn to respond. Perhaps to judge how things are landing as they are speaking?
If this is true one can see how it would lead to misunderstandings. An introvert thinking "This salesperson is making eye contact, but they just keep talking. Why are they so overbearing?" Or an extrovert thinking "This person is telling me terrorists are going to strike the World Trade Center, but they won't even make eye contact. Why do they have so little confidence?"
Anyway, like many signalling mechanisms, I'm sure there is variety across people and cultures.