Facebook feeds:

?a $.$ ?

are limiting the reach of organic posts, prompting many firms to spend on Facebook ads to connect with more users.

?b $.$ ?

prohibit content promoting apps that run outside the Facebook platform, since such content competes with user attention and Facebook wants users to spend as much time as possible on its own services.

?c $.$ ?

ensure that any post from an organization's fan page will arrive in the feed of anyone who has "Liked" that page.

?d $.$ ?

will show identical ads to all users, worldwide, if they are of the same age and gender.

?e $.$ ?

are entirely ad $-$ free. Zuckerberg refuses to run ads in feeds because he feels this will degrade the user experience, even though Facebook would likely earn significantly more if it did so $.$