The weird reason that Facebook will never have a serious spam problem
September 4, 2013 | By Dennis Yu | One Comment">One Comment
Mashable reports that Facebook spam is a $200 million a year business. 4% of Facebook page posts are spam (hard to define), while 70% of email is spam.
Short answer: On Facebook, you can’t send messages to people you don’t know. But you could email millions of people, since context is not required.