I think in some environments, for some products, using XP and other Agile methodologies make sense. Read “The New Methodology” by Martin Fowler for why. However, some promote it as some kind of silver bullet. A panacea. Shelley Powers raises some good points to think about:

…what the makers behind the Manifesto are promoting is incremental releases–the continuous state of beta that we see at Flickr, Google, Yahoo, and other sites. Yup, that’s where it came from folks: agile programming.

The principle isn’t bad: release small, release often, and don’t get stuck in analysis paralysis. However, the problem with the concept is that many applications can’t be released small, and beta is only cool in certain small circles. Most of us don’t want the systems we’re dependent on to be in a permanent state of change, of beta. I don’t want my income taxes managed by beta software. I don’t the hospital lab’s work to be managed through beta software. I certainly don’t want NORAD to use “Radar by Google”.

The release early, release often doesn’t solve the problems of managing larger and critical need software applications. As for applications that have followed this approach, such as Gmail and others of that nature, we’re already seeing a great deal of pushback against features appearing and disappearing without warning, and applications failing, and cute little plumbers popping up saying, “Ooops! Something broke”. It’s wearing thin; it’s no longer so fun.