There's not a lot of data there, but it at first glance it strikes me that they're trying to establish a different way that users pay for maps, one that doubtless results in higher profits for them, i.e.,

"Used up the last of your map credits? Visit our map store to recharge your account."

I'm a user of their products, but not a fan --- when I reported multiple (very significant, blatantly broken) bugs in their Pocket Topo application, they kindly walked me through a work-around for the most critical one, but for the others they just told me that no update is contemplated. And they're still selling it:
http://shop.nationalgeographic.com/product/247/3917/120.html

The two biggest bugs off the top of my head that will apparantly never be fixed: (1) if you have a map of any significant size, the elevation data is bogus, and as a result the ability to look at elevation profiles is broken too.
And (2) UTM coordinates are available, but WRONG --- they must have screwed up the conversion algorithm, but IMO it's horrible that they allow you think you have the right UTM coordinates when you don't.

Maybe I'm just in a grumpy mood, but that sort of corporate approach doesn't make me want to purchase any further products from them.