The 16GB base model wasn't sufficient for the 6/6+, and is even less sufficient now with the 4K videos and 50% more megapixels (which I imagine would be on by default).
In the previous models (5/5s, 4s) the base model provided enough memory for doing most things comfortably. Now you actually HAVE to get the intermediate model to do anything useful (unless you're in masochistic mood). So the intermediate model (costing $100 more) becomes the entry level model.
I would even go so far to say that the 16/64/128GB memory gradation, coupled with the slippery 6/6s (slip and break more often ==> more AppleCare purchases and/or service repair costs) are intentional.
I understand capitalism and all that, but this is just pure greed and they're not doing much to hide it.
The first time I've seen the Luhn algorithm was on a compromised web server. The cracker has put several fake ebay login/registration pages, as well as a couple of Javascript files.
The pages were obviously intended to be used for phishing. However, what really made me go "wow" was the extra mile they went: one of the Javascript files contained methods that took the credit card number from the fake registration page and checked its validity w/ the Luhn algorithm before emailing it to a random email address. If the number was invalid, the user got an error and they forced him to re-enter.
I didn't know about the algorithm at the time (this was around 2005), so I was a bit baffled what the heck they are trying to do.