Most new PC cases have intake fans in the lower front of the case.
Some use a small filter which keeps the dust intake to a minimal...
but I think many do not. The reason may be that since many people
do not ever open their cases to clean such a filter.. it would get clogged
and overheat the entire system.
As for Air-current placement.. Its pretty logical that if heat does rise,
you would be better to put the exhaust higher up. This is one reason
that they put the power supply at the top of the case. (So it does not
add more hot air into the main chamber and that heat rising right up to
the CPU, sizzling it to crisp)
When you try to fight that natural flow of Heat rising... is where
problems occur.
Yes, dust is always a problem with air movement... but its never that
big of an issue. A simple spray of compressed air once a year would
be just fine. A small filter could be placed near the fan inlet too.
(thought I never saw any arcade machines use filters)
Even if you tried to force cooler air into the top... it still would
carry dust into the cab. If that were not the case, then we would
not have to dust high shelves, door overhangs...etc. The dust is
so fine, that it always finds its ways into the air, and accumulates
into nice piles which then attract (static) even more of the stuff.
As for the distributed idea... well.. the real problem with that
is that by adding only top exhaust fans and a few well placed
vents... you may not achieve a good enough cooling rate.
Partly because air is like a fluid.. It may seep in from the middle
and of other parts of the cabinet that are not as cool where the
vents are placed. Thus, the cool air mostly staying below.
Also, components not getting enough airflow from below..
because the air is not moving enough at the bottom of the
case. And finally, even with a distributed non-pressured
system... you will still get good amounts of dust.
In the arcade Im pretty sure all the intake fans blew into the
bottom.. and exhaled through top mounted fans.
Ive learned the hard way, that merely trying to suck out
all the air in my pc did not cool it enough. I lost 5 HDs because
of poor cooling. Heat rose from one drive up to the next... thus
making the top drives sizzle to death. I know for sure, because
it was always the top drive that died.

Now, Ive added more space in-between them, and put large
fans in front of them that blow cool air into the case, and across
their surfaces. Ive not lost a drive since then, and its been
several years time. The case is also twice (or more) as cool
as it used to be.
My case is set up with cool air coming in from the bottom front,
then pushed via another fan thru the CPU heat fins, then exiting
out the rear and top mounted power supply areas. On this med
temp night.. my cpu is a mere 84f degrees. (Core Duo 2.4)
Ive had older setups where the inside of the case was like
a blast furnace. Also, I experienced this on many others
PCs when I had a job fixing them. So, I have good
knowledge and experience with such things.
HDs are the most sensitive to heat. The heads are placed very
close to the surface of the platters. I Believe if the metal heats up,
it will expand...and thus the heads might scrape the surface of the
platters... which will wear and destroy them.
CPUs and other small electronics are also prone to malfunctions
and problems from excess heat.. I believe their traces are so close together,
that if they expand, it causes small shorts.