Now this is something that is difficult to do. To build strong companies, you need strong personalities but so often strong personalities overwhelm the company, and create auras of their own. I see this in many large companies, and even in Google. People in positions with strong personalities become gatekeepers of important processes in the firm. This, in turn undermines the same entrepreneurial nature that brought the company to where it is today.
Be a visionary, but don't become a cult-head. There is a fine difference between the two and the trick is to know where to exercise your power. This does not mean cult-heads do not work. Apple's CEO is probably the nearest one gets to being one. However, using the power to initiate significant shifts in the industry is one thing. I have seen many instances of amazing ideas not going anywhere because the gatekeeper did not like it. This can be exacerbated if the gatekeeper is not in tune with the trends especially if this is a fast moving Internet services industry.
One thing a startup needs to do if it has to survive in today's age, is to avoid the culture of fear. People should be able to question everything and feel like they have a say in things. This obviously should be balanced with not getting muddled in chaos. But there is a way to do things that makes it more transparent and empowers people and yet does not sacrifice efficiency.
In a previous company that I worked for, our projects would get shut down seemingly arbitrarily by the VP. As an engineer, this was incredibly frustrating and demoralizing. I am sure there was a sane reason to shut down the project, but it is as important to convey why the project was shut down as to shut it down. The action of shutting down ensured that the company did well fiscally (or whatever the business reason was). The why (and the true why not the business gobbledegook) is what ensures that the creativity and morale stays high.
Google is sliding from the startup scale towards the large company scale. As time goes by, the whys will becoming harder to discern, and things will look increasingly arbitrary. However, this place is still way more transparent than most places of its scale. And this brings us to the most important tasks of a Product Manager: ensuring that the why of any action that impacts the team is known, and conveyed truthfully and sincerely.
In a startup, the CEO is the Product Manager. And s(he) needs to ensure that the whys are propagated.