well yeah you're both basically right, it's related to the # of platters required to achieve the size you want, and the heat between the platters, and the heat breaking down the "grease" (thermal or fluid dynamics or ball bearings or whatever the hell is in them nowadays)
The limit question was just to quench my desire to stuff 4x750 gb cool running seagates in there (i <3 seagate for life) and they're waaaayy less expensive than the 1tb drives
Typically i try to keep the house ambient between 72 and 76 degrees for the reason of our computer room
here's hoping i can throw a distro of linux on there with the equivalent of windows disk spin down mode when inactive for a while, i couldnt find shit on the snap 4400s with the 2.6 or 3.x os , and i dont know enough about linux to know if that exists but im willing to dig in and find out...that would surely help