The world is dynamic

Design things as such. In particular, beware of constant numbers and remember the Zero-One-Infinity rule. And keep your resources synchronised, unlike Bulldog's marketing department: I got a letter from their CEO about how they're getting out of the residential phone and Internet business the same day as a promo flyer came through the door for...their residential phone and Internet service.

For interesting perspectives in general, watch the Google Tech Talks - download the MP4 files ("for Sony PSP") and your waiting-around-in-the-airport experience will be much improved.