A small communication breakdown is enough for everyone to be working on slightly different things. And then you loose focus.
Growth and momentum are what a startup lives on and you always have to focus on maintaining these.
Losing focus is another way that founders get off track.
It's difficult to get large groups of people, to the extreme levels of focus and productivity that you need, for a startup to be successful.
The other piece besides focus for execution is intensity. Startups only work at a fairly intense level.
So if you want a culture where people work hard, & pay attention to detail, focus on the customer, are frugal: you have to do it yourself.