What hides behind 'Customer Focus'

http://www.paulgraham.com/13sentences.html
Startup in 13 Steps

Two that caught my attention - ‘Focus’ and ‘Let it evolve’

• There are lot of great ideas, especially the ones from customers – keeping focus involves a quick objective look at them and dismissing or absorbing them into the current plan.
• Let it evolve – do the minimum, but find a balance to have a foundation strong enough to build on!