(Author of Linked, and various other cool things. Now at Northeastern University and the Dana Farber Cancer Institute, Harvard.)
When do events take place? When doing things like calculating the capacity of communications system, we assume that it's random, uniform in time, and the timing follows a Poisson process. In reality, communication tends to be bursty: e-mail, for example, tends to be sent in clumps. It follows power laws, and can be mapped as a straight line on a log-log scale. This same distribution is also the case for library visits (measured by checkout records), document printing, web page views, cell-phone calls, and just about everything else we can measure.
Why does life work in bursts? Look at to do lists. We tend to assign priorities to tasks, rather than do them randomly or treat a list as a stack. When you follow priorities, high-prority tasks are completed quickly, and some will be done after a long time: you end up with a power law.
Does the length of the queue matter? No– you get the same kind of behavior.
Random Walks. Lots of things follow random walks, or Levy walks (where jump size can vary). Studies of animal motion follows Levy laws, and humans do too: an analysis of money movement from Where's George also follows Levy laws, as does the motion of cell phones detected from tower triangulation.