Eventually, the main obstacles that VoIP has to overcome may not be technical or economic at all. They re probably political. Communications managers with full authority over all things networkable may choose to go whole-hog with VoIP or may find niche VoIP applications. However, chances are they will find VoIP to be applicable somehow to their organizations business needs in one way or the other. On the other hand, those who don t have ownership over both the voice and data side probably will not want to hassle with the internal politics that VoIP engenders.
People make decisions based on many factors.
And for VoIP, corporate politics is still one of those factors.