Assuming the content model is well defined and the content has been gathered, populating the site with content should be a straightforward task. The problem that normally occurs at this point is two-fold:
No-one is assigned to actually enter the content into the system; assumptions are made that the developer will enter content while the developer assumes the client will enter the content.
When content is entered, the gaps in the content model become obvious and either more content must be written or adjustments need to be made to the model.
The most common outcome is that content simply doesn't exist. Even though the model was defined upfront, and someone was assigned to gather the content in the right format, there just wasn't enough content or when the content was gathered, the structure wasn't consistent, e.g., it was assumed that for all distributors there would be a head office and multiple warehouse locations, but when the content was gathered, for some distributors...