Amherst College, in western Massachusetts, enrolled 438 first year students this fall, for a total student population of 1680+.
Here some findings from the school's head of IT.
By the end of August 2008 the total number of members and posts at the Amherst College Class of 2012 Facebook group: 432 members and 3,225 posts.
Average number of emails received per day: 180,000.
Percentage of email that arrives on campus that is spam: 94%.
Full data here - it's interesting. Found by Clive Thompson, and linked by Nicholas Carr - both have comments.