Image via CrunchBase

Pretty much every website you go to tries to provide you with a customizable experience. Amazon suggests other items you may be interested in – based somewhat on what others buy but also on what you’ve bought, what sites you’ve visited, any cookies your browser may have, etc.

Facebook takes into consideration which links you click on and which posts you like, and then displays more updates from those friends and fewer updates from other friends. This may be good or bad, depending on whether you want to stay in touch with everyone or you want to just see what you care about most. (Compare this to Twitter, which may suggest users, but leaves it up to you to manage your actual feed.)