Why are bricks positioned vertically over windows and doorways?

I hate linking to Wikipedia, but usually their articles are well-developed. So here’s what I found: http://en.wikipedia.org/wiki/Arch#Technical_aspects

As far as i know it’s because that way the weight is better distributed, preventing it from falling all on the door/window and instead loading the wall on the sides of it.

@shadling21 s Wiki link says what I was going to, but much more comprhensively.

It also makes a nice decorative pattern.

@Thammuz
That makes sense for an arch, but not for straight horizontal layers.

I think this is an interesting question I never thought about before. :)

@Fyrius well, sort of, the vertical bricks are harder to push down because they press against eachother, when one is pushed down the others tilt towards it thus tightening around it and making it harder to push down. At least, that seems likely, we have lots of brick constructions here in milan but i never really bothered asking my teachers when we were out for art/technical education “excursions” (If it is appropriate to define “excursion” going around the neighborhood looking at old buildings).

@Thammuz
I see. That does make sense.
Cool.