He does say 8gb is fine for normal users but for "Professionals" who require a minimum of 8gb+ will most likely spring for the 16gb. This is my take on on the issue:
1. If you're a "Professional" who using Pro 64-bit apps, runs a few VMs, deals with large raw image files, does hardcore video editing and can take advantage of "AND" needs the 16gb then by all means, get the upgrade. But I think it's safe that to say that's the minority who will require the 16gb.
2. If you're suffering from OCD, get the 16gb, it will let you sleep better at night.
3. OS X has great memory management but with more and more Pro apps moving to 64 bit who can utilize the ram, 16gb is a nice option.
I'm returning mine to the store due to a screen issue but I've already order from the online store and yes I upgraded the base model to 16gb because I'm OCD and will sleep better at night

and the fact I have to run a VM all day, Coda 2 (very large multiple projects open seem to soak up a ton of ram), work with multiple Photoshop files (usually 5-10 open pushing around 100-500mb per file), light FCPX work and the occasional netflix running in the background.
final thoughts:
Most will probably never see a difference or ever require the extra ram, save the money and take your lady out to a nice dinner.
Even with pro apps, 8GB is plenty. I can't get over these people who say 8GB is not enough. I run my business on 16GB on a 2011 model, with SSD and use every pro app you can think of, and only use 6GB at a time with a heavy work load.
That is very rare. Close out your apps you are not using. You don't need 20+ windows open at the same time. Seriously. 8Gb is plenty.
I had the retina MBP and returned it. Might pick one up again because not having the screen is bugging me, but at the same time I can't use it for work space on the go at this time. It just not ready for prime time. Regardless I am on the fence on buying one again just because.
The benefit of the base model, and this is lost on most people, why I can never tell. Is that the base model will allow you to 'swap' out the laptop if ever you need to repair the machine. As nothing is replaceable basically, except for the SSD, it will be treated like a iphone or ipad. Either that or guy the upgraded model, non-BTO. So you can swap it out.
Try swapping a BTO, isn't going to happen. You will have to wait for your machine to get repaired, instead of getting a 'new' or 'refurbished like new machine. Being a business man, I don't have time to wait. I need my machine now.
Go with the pre-configured models, especially since the RMBP cannot be upgraded or fixed easily. Battery anyone?

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you can never have too much memory! period!
I have had work stations with 48GB ram and render servers with 72GB ram.
8GB for serious graphic design is nothing.. either you work in low resolution or you only open 1 image at the time.. which.. well that's your choice.
16GB is by all means the way to go, no matter if you are a graphic designer or not.
Oh brother.
Please. Just stop it. 72Gb of ram on a server, but you are not going to ever use the amount of memory a server needs or uses. 8GB for graphic design is plenty. Serious work, how about editing videos for NBC, FOX, CNN, or graphic design for advertisements for Apple, Nokia, Samsung, LG, Panasonic? In their board room or at a fancy restaurant in front of their marketing executives on a laptop no less.
Is that heavy enough for you?
Your machine will not blow up if you don't have 16GB of Ram. I have 16GB of ram on a 2011 model with SSD. Don't hardly use 8GB if ever. Close out your apps. In the future like 3+ years from now will 8GB be enough. Should be. Maybe not. If you plan on keeping it more than three years, get the 16GB. 8GB will be enough three years from now. Longer than that, maybe not. But for now it's enough depending on your usage.
Mountian Lion doesn't use up as many resources as Lion. More efficient use of memory usage. Is it always better to have more, sure. Is it necessary. No.