Posted to firstname.lastname@example.org in response to a thread about SharePoint vs. Google Apps for a small church organization:
I think about SharePoint in the following terms (YMMV):
SharePoint at its core is web-based file sharing. Conventional LAN file shares have some major drawbacks: you have to be on the LAN to access them, and it's difficult to include and utilize metadata. and. SharePoint began by addressing these two issues. [Today's SharePoint also includes document management features like global search and workflow.]
If you ask, "Why do people share files?", the short answer is, "They're collaborating". So SharePoint includes collaboration features like check-out/check-in, announcements, calendars, and discussions. This is the basis of the "teamsites".
It is common in today's project-oriented workplace for people to work on several project teams. Some integrated view of multiple teamsites is needed, so SharePoint includes portal features like MySite. [Today's SharePoint also includes "social" features like "Colleague Tracker".]
Now that SharePoint is collecting all those eyeballs, it becomes attractive as a business application platform. Data views, Business Data Connector, Key Performance Indicators, and so on follow.
With so much web-based business function co-located on the SharePoint platform, it is also attractive to integrate content management; hence the Publishing feature.
So you can consider SharePoint an integrated suite of web-based applications for file sharing, collaboration, business information, and publishing. If all you need is file-sharing, there are simpler alternatives.
Alex is exactly right: details are king. The problem is that the details of the work that people need to do are often hidden from the person who makes the decisions about what platform they will use.