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By “going wide”, we raise our chances of hitting on the best design. We start with several candidate trees, then use a reliable method (tree testing) to choose the best one.
For more on this, see Jared Spool's short article on exploring multiple variations.
Data for the CEO
Consider also that the “other members” that you get input from might include the CEO. And (trust us), if you need to shoot down their out-of-left-field idea, it’s much easier to do that with objective data from testing than just your personal opinion. 
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