Here I put the top five from the list and added my own observation and experiences.
Number 1: Confusing Customer Requirements with Product Requirements
Many products are built by working closely with one or few customers. We let the few customers to drive the key features. It is a good to gather customer requirements to establish the product requirements. However, we need to make a differentiation of the requirements specific to the customers from those for everyone.
Number 2: Confusing Innovation with Value
This is another extreme. The product design is engineering driven. There are good idea from engineering teams. However, we need to make sure that the creative feature are solving the real business problem. Sometimes, the product is over engineered with a set of features which nobody is using.
Number 3: Confusing Yourself with Your Customer
Some of us believe that the product manager himself or some upper management know what the product requirements are. We use the internal source instead of the customers to validate the requirements. What we come up internally are just assumptions. Assumptions need to be validated to be the true requirements. It is very dangerous in my opinion especially when we face someone internally who pretend they know the product requirements and make very assertive calls.
Number 4: Confusing the Customer with the User
This is mistake happens because we do not focus on the big picture but only on the small product features. The day to day direct users focus on how to make their job easier but may not tell you what process can be automated and what jobs can be eliminated.
Number 5: Confusing Features with Benefits
Customers want to get the true benefits not just a set of product features. The product features need to provide the benefits to them by solving their problem. Adding features to the product do not always mean providing the benefits. They are other important things - quality, simplicity, extensibility, configurability, scalability, etc.
There seems other good stuff from Silicon Valley Product Group. I plan to read them when I have time.