Much too often, projects fall victim to the “scope creep” syndrome where the project scope expands with disregard to the scope that was originally agreed when it was first chartered.
This often causes many problems inside and out of the organisation. For the organic project team working within the organisation, they will find that tasks are constantly being added to their plate in a never-ending stream and the project sponsor/s will constantly be hounding them on why deadlines are not met — even when the original deadlines were established without the new additions to the scope!
Exernal to the organisation, the vendors will also face problems as they will be caught between the wall and a very hard place: risk annoying the customers by refusing to add to the original project scope or take on the additional scope and overallocate resources beyond the original budget?