It wasn't a big project, I was the sole coder. What had been sold in was basically a Drupal install with some customization. I made sure they wrote a decent specification before I accepted the job.

I delivered on time and we had the first test with the client. Everything went very well, and the client seemed happy.

On the client side, the project was then moved from the project group to those who'd actually be using it. And then came the question from the new manager:

Mgr: "This looks nice, but what about all the other sites?"

Us: "Other sites? The contract was only for one site."

Mgr: "Well, the whole point here was to have 17 sites with site-specific content written by site-specific users, managed centrally with a unified look as if it was one single site."

Us: "Err... that's not what the specification we agreed on says."

Mgr: "Well, as it stands this is useless to us."

And so the simple three day job turned into many weeks.