In reply to a post by Marcel Paschoal on project methodologies I wrote a short comment:
The core problem of waterfall: You forget an item in the planning and that will haunt you for ever in the development phase.
The core problem of agile: Just because you add slices (sprints) on top of each other you don’t necessarily build a Tour d’Eiffel but rather build the leaning tower of Pisa (that eventually crumbles).
You need a healthy mix of wider planning and agile implementation.