Over 30 million accounts on Facebook belong to dead people.
There are cases of people being murdered for unfriending others.
In 2006 Chirs Putnam hacked Facebook, changed 1000s of profiles to a MySpace style before he was hired by Facebook
Burger King had a campaign for a free Whopper if you unfriended 10 people and sent them a message to let them know they were worth less than a burger. The campaign was quickly suspended.
Source: The Washington Post, The Guardian, The New York Times, Base Line, NDTV, New York Daily News, Inquirer, The Telegraph, Forbes, Business Insider