h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The 80/20 rule applies in a very large number of situations in the IT world, e.g.:
20% of the functionality will take 80% of the budget/time to accomplish leaving the remaining 80% of the functionality to be hashed in in 20% of the time. Unfortunately another 20% of the time will be spent working out how we can get the remaining 80% of the project done now that 80% of the requirements have changed and 80% of the staff have left for pastures new. Usually this involves 20% more managers and 80% more meetings so the project gets delivered 80% over budget and with a 20% failure rate .