A 2010 National Geographic video talks about 7 billion people (the Earth's population at the time). At timestamp 1:57, the video claims that
standing shoulder to shoulder all 7 billion of us would fill the city of Los Angeles
Some rough math I did using the land areas of the US state of Oregon (248,849 km^2) and the city of Los Angeles (1215.97 km^2) from Wikipedia suggests that you would need to fit ~28 people per square meter to get everyone to fit in Oregon and ~5676 people per square meter to get everyone to fit in LA.
This seems impossible, even if you limit this to the adult population (4.630 Billion as of 2005, according to Wikipedia), you're still hitting ~18 and ~3807 people per square meter in those two areas respectively.
Is there some other way they got to this number that I'm not seeing??