Facebook’s new ‘ticker’ gives you a rolling real-time list of what your friends are doing. The problem is the result of the lax or non-existent privacy settings of your friends. If you want to stop strangers from seeing everything you do, you and your friends need to change your privacy settings to Friends or custom lists. The hard part is getting your friends to do it – and make your friends do it too. Anyones posts which have privacy set to more than Friends will go to all the friends of all the commenters.”]
Source: https://nakedsecurity.sophos.com/2011/09/26/facebook-ticker-privacy-scare/