Adding manpower to a late software project makes it later.

Obstacle #1: Naive Resource Management
Obstacle #2: Teams Organized by Functional Specialization
Obstacle #3: Teams Organized by Architectural Components
Obstacle #4: Distraction
Obstacle #5: Reluctance to Continuously Refine, Reprioritize and Rescope
Obstacle #6: Rampant Technical Debt
Obstacle #7: Lack of Commitment to Transformation