Martin Fowler discusses Technical Debt. Taking shortcuts in design or development is like borrowing from the future. You save time now, but will have to pay later. Eventually you’ll have to put in extra effort to deal with your old hacks. This extra effort is the interest you pay on your technical debt. You can take time later to fix everything, which is analogous to paying down the principal on your technical debt. It costs real time now, but saves you interest payments in the future.

As with most interesting ideas about software engineering as a discipline, Ward Cunningham’s apparently infinite wiki has a page about Technical Debt.