Totally agree.
I looked in to the operating temperature specs for a lot of HD´s some time ago, and even though I can´t remember the exact figures, the newer (Seagate 7, 8 &9) series runs hotter than the older ones. (Of course, I will say).
In my own case, if I move my HD-fan 1/4 inch up, my Seagate 7200.7+ gets up to 8 degrees celsius hotter, because of the "hotspot" in the middle of a fan (most fans out there). Don´t point that "hotspot" directly between two HD drives - as there would be an airflow of next to nothing compared to at the fanblades themselves.
Almost the same applies to the distance between the fan and the HDs. If the fan is like 2-5mm away, that same hotspot fills a big area in front of the HDs. Make at least 2-3cm between fan and drives, so the air can come "into action".
Another hint: Fans in the front should blow a little more air in to the case than is taken out on the back. Side ventilation is not always for the good btw. : In one case(!) the HD´s ran hotter with the sidefan installed compared to a sealed off hole... until We (my friend and I) got a lowspeed model (<1000 RPM). What happened is that the air taken out by the PSU got delivered by the sidefan, so the front didn´t get helped by PSU sucktion, which made the HDs hotter. Now with lower sidepanel speed, it works beutifully!
(OK, one actually don´t need side cooling for the most, unless it´s for cooling a passive cooled graphics card, or a motherboard, where the tiny little wheeeeeeeeny fan is exchanged for a passive one)
Allthough I don´t consider myself Engineer Of Them All, It didn´t take me long to realise that cooling of computers almost is an art in itself!
Today my main machine (used for making music with upto 32tracks HDrecord from one disk), allthough cooled by airfans, was measured with a professional neutrik sound pressure meter and runs at Max. 19db at ear distance (~60cm) Temp.@ CPUmax(XP1800)=42 celsius, HDmax=34celsius, ChipsetMax=29celsius, Zalman-surfaceMax=30.
(And no, I don´t use a sidefan for the Zalman cooled 9600Pro
And now I´m out of ink
Doom thee who don´t cool proper in that case!!