The problem with agile is that it is a greedy algorithm. It can lead you to local optima. Usually this is not an issue if you are doing contract work, However

The problem with agile is that it is a greedy algorithm. It can lead you to local optima. Usually this is not an issue if you are doing contract work, However, if you try to create a product in a market with competition, a non agile competitor can reach a global optima (for example Apple vs MS in mobile phones), and than you will lose the market (and sometime your future).