I saw an interesting survey on LinkedIn asking,
“Is SharePoint equipped to cope with complex line of business document management applications?”
Unfortunately, I had to answer “No” to the question, but the simple answer and the nature of the question can be a bit misleading.
I make my living implementing SharePoint systems. SharePoint does very well as at providing a platform for implementing document management applications, but is not a great product for advanced document management.
To provide some context through an example, I have helped implement SharePoint for a government organizational unit with over 20,000 internal users. This organization has been using SharePoint as it primary knowledge management platform for over 4 years and has started developing applications on the platform. They're content repository is about 2TB now, and they anticipate growing that to about 6TB once they implement formal records management in SharePoint. 77M documents per year is not an issue if the system is architected properly (good storage and information architecture, and governance plans).
That is an enterprise-scale implementation by most definitions. That said, the scale of the implementation says absolutely nothing about SharePoint's capability for advanced document management; scale has nothing to do with complexity. I.e, I can easily dump 10TB of documents onto a network file share, but that doesn't give me a "complex document management application. Document storage is only a small part of creating a document management application.
The piece that SharePoint is missing is missing, and what we help customers implement, is the document processing component on top of the very scalable document storage infrastructure that SharePoint does offer. Microsoft has taken some steps to filling the gap with the introduction of Word Automation Services in SharePoint 2010, but there is clearly a long way to go.