I have been involved quite a bit lately with mapping Customer Journeys. Just in case you don't know what that is, it is a simple concept: Every customer goes through a number of steps before they purchase something, and this journey sometimes also continues long after the transaction.
Most companies have a very rough model for the customer journey, usually linear, where one step advances to the next one.
Reality is, that most customer's journey is almost never linear. As they progress, they may go back and do some more research because they become more educated, which brings in additional decision points
The journey is usually more tortuous and long the more complex and pricey products are. Let's say you are considering buying a new computer. It may be that you start the process making an inventory (written or mental) of the features you require. Then, it is very possible that you will visit a website where you can compare side-by-side some computers to get an initial idea of a price and available features. You may adjust your requirements and your budget after this. It happens very often that this initial search leaves you with more questions than answers, which will make you read a few articles online, investigate about certain new technologies, talk to a friend, and maybe even visit a store. Finally, you make a decision and you buy the computer of your choice. Then another important part of the journey starts, which involves setting it up, etc.
What is really astonishing is not recognizing this, and being surprised when the customer doesn't follow the plan. As a good friend says often "all models are wrong, some are useful". In this case, the map gives us a usual model, but the map is never followed.