Prioritizing Requirements
This section really reiterates what came before: you should be building software that your users need in preference to what they want. That's the ideology, anyway. Reality has this annoying habit of chipping in with a "well, actually" at this point.
It's much easier to sell the thing the buyer wants than the thing they really need. Selling things is a good opportunity to take, as it allows you to fund other activities: perhaps including the development of the thing that the customers still needs. But, well, actually...
...good marketing efforts can convince the customer that the thing they actually need is something they do in fact want. You can then shortcut all of the above discussion by making the thing people should be buying and convincing them to buy it. This is one of those high-risk, high-reward situations: yes, selling people a faster horse—http://blogs.hbr.org/cs/2011/08/henry_ford_never_said_the_fast.html is easier but the margins...
