In the book Steve said when a project falls behind, the most logical thing is looking to see which scope can be delayed for next phase.

Actually the big projects I worked with (from six months to 2 years)

The most common reasons why it fell behind were

1.   Project planning and scope was not clear, business users could not decide what they wanted.

2.   Incapable project leader - happens all the time (actually it is happening at my current project)

3.   Incapable developers - had the wrong persons doing the wrong jobs.  SQL deveopers could not right SQL code. SQL DBA did not know what he was doing.

4.   There should be a change control in place, at a certain point of time, the project leader had to evaluate the change control should be put in the project or delay for the next version.  I remembered in my old company the users wanted changes at the end and the manager agreed to do it.  The testing was not thoroughly because of constant changes and after it released into production, the system had so much problems even the CEO noticed and was so upset.