I think they were smart to start making some deviations from the main story early on.
First, it gives the readers a reason to keep watching since they can't be sure that what they've read in the book will necessarily happen in the show.
Second, it establishes early on that there has to be some differences simply to accommodate the different format and signals to the fanboys to be prepared for the changes that may be required when anything becomes a TV series.
For example, by necessity they are going to have to change things about Carl simply because (unless they keep recasting the part), the kid is going to obviously age during filming and between seasons (not unlike the Walt problem on "Lost"). Whereas Kirkman had the opportunity to tell a story of a few days or months over several years without his characters aging, a TV show doesn't.
Given that sort of real world production issue, I can easily anticipate that the TV series may adapt some major plot points but drop others. As such, they were smart to quickly send a message that this is not going to be a point by point retelling of the comic.
