As I understand it, the underlying data has no time component (i.e., we don't know on what date the person moved; just that they moved). Therefore, showing a stream of particles moving out of a city brings in an (erroneous) time aspect to the move. For example, you see one city lose its population; and then a minute later, people start flocking to it. There is no temporal causality here, but the visualization projects such.
A better way would have been to project all the moves along the same time axis, and show them all at once.
Another idea: plot the delta (gain - loss) for each city as a circle; make the size of the circle a function of the magnitude, and the color a function of the sign.
You can also slice-and-dice by demographics and income (like the video did towards the end), and just show those numbers. (Which cities gained the most millionaires? Which cities gained the most youth??)
As you point out, aggregation and faceting both solve this, but I really wanted to show all of them. That has more though to do with creating an experience of having seen a certain phenomenon than creating something actionable and clear. It's self indulgant, but I like that. And I agree: static representations with aggregate data would be interesting.
Is there some software that can generate that, or was it done the old-fashioned way, by filming an actual terminal?
A good visualization should convey something even to those without any domain knowledge.
A damn fine visualization, though, can still require domain knowledge. For example a medical plot is an excellent visualization of certain parameters, but it does not tell much to a non-doctor. And there are plenty of extra useful visualizations in the sciences that only makes sense when you have extensive domain knowledge -- like most of the plots in engineering papers.
How about a "visualization of C++ programmers migration patterns away from Norway", after the whole Nokia/QT fiasco?
Why the downvoting hate bros? I love QT, I just wish Nokia had a real vision for it so that it's future is assured.
P.S Except if its for the off topicness, in which case, downvote freely.