Comment by Aqueous

Perfectionism is a pitfall, but agile development has led a lot of developers to prize velocity over correctness. Many seem to believe that any upfront mistake can be fixed through iteration. The truth is that there are things that you can't fix through iteration. Things like having an incorrect data model. Some things need to be perfect up front or you will quickly find yourself boxed in down the road as you try to extend the system. Once you've gotten the right design at the center of your system, understanding not only the current requirements but also likely future requirements as well, scrum away. It's just not OK to blow the "big picture" decisions that you need to do in order to build a piece of software the right way because you want to move fast.