How to balance being nimble with being productive? Scaling a company.

Now it seems to be a general consensus that working the at a small nimble company with a startup atmosphere is "our" ideal working environment. Its the environment that promotes our creativity, and allows us to work with the least amount of useless bureaucracy. If you disagree or have different preferences, please share. However, all companies want to grow up as well. It seems to be another general consensus that large unwieldy companies are not as good a place to work for conditions are opposite as mentioned above (see microsoft, google, yahoo etc). So how do you balance this? How can you balance this in a business? At some point you need more employees, but once you get too big, you become unwieldy. Its a paradox.