All the js/css/other stuff facebook includes on their homepage (one server round trip each).

Before they spent the millions it takes to bring up another data center they should have read this:

http://developer.yahoo.com/yslow/help/#guidelines

Also, I disagree that 70ms makes that big of a difference. People are more used to slow sites then people realize - anything less then 200+ ms improvement in the aggregate and I wouldn't spend a dime (not to mention millions of dollars).