I think it's important to have one person that says the final 'yes' to all the decisions in a start-up.

That one person should be the visionary leader because they can see how their 'yes' will set off a chain of other opportunities for the company in the future.

Some of these decisions may be perceived to be risky, or stupid.  But risky or stupid is better than boring, banal, copy-cat compromise that other companies are doing.

It's important though, that the visionary leader listens, and is able to give up their ego if someone has a better idea than them.  Because the leader isn't the only one with good ideas.

At the end of the day though, if a start-up wants to be a lean, mean, fighting machine to achieve its goals, all parties in a team have to stay the course with the agreed-upon plan.  Otherwise, rather than streamlining through the water, you'll be floating along with the waves.