who the hell needs 16 GB of ram. Jesus christ. Unless you are running video software, my 2 year old i7 with 8 GB ram can handle just about everything I throw at it.
Most people probably don't need more than 8GB (at least for now), but I personally need at least 16GB (I have 18GB on my Mac Pro). I often have two Parallels virtual machines running, XCode, Aperture, Photoshop, and other applications and if I'm not careful I have got into situations where my performance dropped due to paging.
I'm going to buy myself a new 27" iMac to replace my almost 5-year old Mac Pro, and I'll probably get the 16GB of memory directly from Apple (and buy OWC memory if I ever need more). Looking at the upgrade pricing on the Mac Mini, going from 8GB to 16GB will cost $200 vs. $130 or so from OWC for 16GB. I'm willing to pay a small premium for Apple memory.