Some thoughts (which may or may not be half baked, as my knowledge and experience with SP is limited)...
* Isn't storage of documents inside of Sql Server more expensive than on disk?
* Isn't document sharing about the least $$$ profitable reason to implement SharePoint? How does that provide a return on investment?
* Since Search can now catalog files on disk, and with full text searching, why bother "cataloging" manually by providing tags and the like?
* Some reasons you might want to bring docs into SP might be SOX, HIPAA and other secure access issues.
* SP requires an expensive person to configure and maintain, so you need some $$$ impetus ore a need to satisfy a requirement.
* The best stuff is only in Enterprise, (ie: PerformancePoint dashboards), and that costs a lot more, so you need to be sure you can't service your stratgic decision maker(s) any other way just as well. SSRS can provide report subscriptions, for example.
* If indeed, SP is the future, *which I think it is*, since it is web based, then it is useless to resist the Borg. But like the Cloud, when must you surrender? Maybe not for three years.
* Organizational tools are wasted on people with no knack for creating effective teams to begin with.
What I lack in youth, I make up for in immaturity!