Jared Spool in The Value of Appl’s Knowledge Navigator: Gruber Has It Partially Right:

When teams don’t have a vision [“¦], each person is walking around with a different understanding of what the end of the journey should look like. When ther’s no common understanding on what that end point looks like, each decisions is evaluated on a different criteria and the resulting products end up looking like crap.

This is why I believe that product roadmaps are not evil. As I’ve written before, at our company we are very clear that the product roadmap is a flexible guideline that can (and must) change frequently as needed. But it gives the teams (and the management team) something to work towards. It’s a common vision, a sense of direction that’s more than just fluffy language – it’s concrete evidence that w’re headed somewhere good, and we know how to get there.