Facebook messenger or maybe they have a Facebook game running. Could be they have nothing else to do that day.
Agent Derek B.
One reason is because he or she wants to be active on Facebook all day long. In some countries, folks get to do what they want when they want.
Maybe there Job Requires to be on Facebook some people Manage there Company's Facebook Page other then that there is also a Possibility they may not really be on Facebook all day some people leave there Facebook Open without closing it Facebook does not go Idle
Nothing to do and the need for constant small new information that fools oneself into believe he is catching up or doing something useful, that feeds itself in a vicious circle that stops these people from doing other meaningful and exciting groundbreaking work such as answering yahoo answers.
Someone is creeping
Plenty. Having enough free time for starters.