MarkoH01: It happens in IT. When I worked as a database programmer in Delphi a long ime ago they only had two people left that were able to work on their old projects already sold to customers because nobody else still knew the engine/language.
And only in a perfect world everything is documented as it should be of course. Depending on the quality of the programmer/firm it might not be that perfect.
Oh for sure, I've taken over a few projects from other programmers that were complete nightmares. I'm just saying, as a company you should have some coding standards and if you don't... adopt them... now.
Plokite_Wolf: This. Many programmers in general don't have the will and/or time to make complete documentation. And by using "seasonal" technologies as is often the case in web dev, there will likely be nobody left to understand that code even with documentation by the time the original authors leave the company.
Speaking as someone who does web dev, I document pretty much everything, but then again I had a professor in college that was really strict about making comments & documenting stuff. Missing a period would lose you points. So to me it's kind of natural.