When faced with a complex site, a lot of web companies cobble together previously used and third party code.
They build the site in their GUI of choice (DreamWeaver, GoLive, etc.) and then add on task-specific code from other sites they've done and/or from 3rd party developers... plugging in an e-commerce engine, forums, photo module, submission forms... you get the idea.
The result? A cobbled together "Frankensite" they don't really understand.
Are you building Frankensites? Ask yourself...
Were the modules all designed to work together?
Can people tell by looking at the site that it was stitched together?
Do you know what to do when tab A stops working with socket B and something breaks? (be honest...)
Say goodbye to Frankensites... and tell those torch-wielding villagers to go home.