All repairs tend to destroy the structure, to increase the entropy and disorder of the system. Less and less effort is spent on fixing the original design flaws; more and more is spent on fixing flaws introduced by earlier fixes. As time passes, the system becomes less and less well-ordered. Sooner or later the fixing ceases to gain any ground. Each forward step is matched by a backward one. Although in principle usable forever, the system has worn out as a base for progress.

The Mythical Man-Month: Essays on Software Engineering, Anniversary Edition (2nd Edition) by Frederick P. Brooks

ISBN: 0201835959 This book is available from Amazon