Monolithic Spaghetti
Great quote from Rick Jelliffe on the xml-dev listserv (found via a pointer from Tim Bray - thanks, Tim!):
Once a large technology is made from sufficiently intertwined parts, there is no way to order an exposition of it such that strongly-connected ideas are always close together.
Spaghetti doesn't want to be free.
The current version of the-software-that-runs-CAREO has suffered pretty severely from this spaghetti syndrome. We're planning the next version, which is a complete rewrite, to be much more modular. Using smaller bits of functionality, hopefully nothing reaches the spaghetti critical mass.