1. VMware + GNS3 to simulate an 2 active directory sites, with a WAN between them - is my personal use case where the more ram the better.
2. Alternatively, simulating trust relationships between AD domains, development lab for Exchange upgrades, etc.
There are plenty of uses for 16gb of RAM or more, if i had 32GB in my laptop i could certainly make use of it. I'm constantly hitting the limitations of 8GB at the moment at work and am likely to pop 16GB in my home machine (the MBP below) shortly so I can get things done at home instead.
Having a heap of RAM in my personal laptop means I can simulate a hell of a lot of stuff without needing to build a test lab.
That's exactly it. The use for 16 gigs of RAM, or two 6 core CPU's in a Mac Pro, or a retina display on a laptop, are limited to certain needs.
What 95% of people do 99% of the time on their computers could be done with an iPad. It's what 95% of people do 1% of the time, or the other 5% do a little bit more often, that demands a desktop class computer (including laptops these days), faster CPU's, more RAM, etc.) Even some who push technology to the limits STILL check their email, browse facebook, check internet forums, shop online, etc. All things any cellphone from the last 5 years (or more) can do. It's the once in a while, niche, odd, intense situation you need it for.
Or, in the case of RAM, simply because the cost (when you do it yourself) is so much minimally more than an 8 gig upgrade.
In my own personal use though, it's being able to run applications like photoshop, while simultaneously running Linux and Windows 7 in two separate VM's on separate desktops (swiping between them like desktops, such a great way to use the 'full screen' apps feature!)
I could squeeze that into 8 gigs depending on what apps I'm running, or spill over into Virtual memory, but, when it's $20 more to go to 16 gigs over 8 gigs, why the heck not? It allows me to do those rare, once in a while tasks like that. Or, heck, just be lazy and leave the VM's running even when I'm not using them. It's easily worth $20.
Plus, I've got a 500 gig SSD (well, two 256 gigs in RAID 0), and I use about 120 gigs right now. How silly would it be to have a 128GB SSD, then swap it to a 256GB SSD when that gets full, etc. etc., Why not just get setup with 500 gigs of storage knowing that, down the road, I might use it? Again, the costs of buying it all at once is cheaper than incremental upgrades.