OK, random thought experiment. As someone without a facebook it's hard for me to evaluate, but how much damage would really be caused if facebook just disappeared one day?
Absolutely zero. People would find another way to communicate, socialize, or whatever. The loss of Facebook would be a loss of jobs and income for people, but that’s it. Facebook serves no positive purpose in society, and it seems the best thing a person can do, is to delete their Facebook account.
2. S&P 500 will go down 2.5% the very instant FB disappears. Further consequences for financial markets are hard to predict.