The Closer You Look, the More Complex it Gets...
Over the years, there have been many analogies proposed to help people understand the sheer depth and breadth of SharePoint. Application, Platform, Pie wedges, Donuts, Layers like an onion, Shimmer ("Floor wax and a dessert topping!"). A few years ago, I used the parable of "The Blind Men and the Elephant", and that was looking at the much simpler (relatively speaking) SharePoint 2003!!
Today, SharePoint Server 2010 is orders of magnitude more comprehensive. At the most superficial level, you can look at the whole of SharePoint, and see organization and structure. The key areas are fairly easy to identify, but maybe a little fuzzy around the edges. Consider the image below, which represents the "complete" Mandelbrot Set - the classic fractal example.
Mapping this to SharePoint, you might see the large, two-lobed central area representing the Collaboration and Content Management features, the large ball to the left as social, and other balls representing Excel Services, Access Services, Search, etc...
But when you get closer, and start exploring some of the deeper capabilities, things don't get any simpler. Let's say you want to start exploring the integration of social tagging with content management, so you zoom in on the area just above the center of the image, between the two larger segments. Suddenly you open up a whole new world of options in API's, storage requirements, user interactions with news feeds and tag clouds, managed metadata and tagging external content - all in just that one small area of SharePoint functionality!
This same expansion of detail and complexity occurs virtually anywhere you look. And although every area you zoom into is clearly related to the whole, each has its own variations in the detail. This is why I am using fractals, rather than layers, to describe the depth of SharePoint. While each aspect has levels of functionality (from basic web UI to development APIs), each set of levels is slightly different. The social APIs look different from the search APIs, which are different from the publishing APIs.
That's why it is so hard to find anyone who knows "everything" about SharePoint - it can't be done. People tend to disappear into whatever rabbit hole they find most interesting. Now that doesn't mean that a single person can't know a lot about many different areas. But, you can pretty much guarantee that they don't know everything about everything. There is a very strong tendency to specialize, and even the specialists are (if they're worth their salt) constantly learning.
Oh, and just so you know, the detail image at the top of this article is about the same fraction of the image immediately above as that image is of the entire set!
Note: The fractal images in this article are derived from those in the Wikipedia article on Fractals, and used under the Creative Commons Attribution-Share Alike 2.5 Generic license. They were originally created by Wolfgang Beyer with the program Ultra Fractal 3.