When is it too big?

From the official Facebook Blog and the owner himself:
A Great Start to 2009
by Mark Zuckerberg Today at 4:37am (Jan. 6, 2009)
“Today, we reached another milestone: 150 million people around the world are now actively using Facebook and almost half of them are using Facebook every day. This includes people in every continent—even Antarctica. If Facebook were a country, it would be the eighth most populated in the world, just ahead of Japan, Russia and Nigeria.
When we first started Facebook almost five years ago, most of the people using it were college students in the United States. Today, people of all ages—grandparents, parents and children—use Facebook in more than 35 different languages and 170 countries and territories.
The full potential of the web is to make the world more open, so everyone has a voice and can share what is important to them. With 150 million voices and counting, we can’t wait for the rest of 2009, and we look forward to offering even more ways for you to connect with the people who matter most.”
It seems to be growing very fast. FB hit 150,000,000 just about two months after reaching 120 million and about four months after reaching 100 million. The site hit 140 million in the middle of December.
When is it too big? I hear Google didn’t partner with Yahoo! because of potential Justice department concerns. Governments worried in the past about IBM, Microsoft, AT&T. Who’s next? How many customers / participants represents too much control?
Hmmmm.
Stephen