In Dee's excellent review of an Antec case, there is the mention of 'negative pressure' because of the large number of exhaust fans.
I think blowing cooler air onto hot devices is a superior cooling method, rather than 'exhaust'. Both are important but since retail PC cases aren't air-tight, I'm not sure how valuable 'negative pressure' is.
Since many cases are now coming with two top-exhaust spaces, I've wondered if the traditional back-of-case exhaust fan shouldn't be reversed and blow additional cooler air towards the CPU and over it, past the RAM slots, leaving Top Fans as the only exhaust.
I also think that a changing fan-speed would create greater turbulence (changing air-flow) inside a case, which should - theoretically - be beneficial rather than having a set number of 'eddys' pooling up, always in one area inside the case.
But no, I don't look forward to little mini-rotating room fans whirring left then right, then back again...
The base question becomes - "Why not have most of the fans blowing INTO the case and only a few top-exhaust fans?"
(By the way, on Dee's Antec review, something that Antec excels in is the air-space between stacks of HDDs. I just wish their rail system was TINY so this air-space would have far smaller drive-bay reflective anti-airflow 'faces' near the chin-fans.)