Facebook's drill button would be hidden in a huge list of other buttons, the order of which changes randomly every time the page is loaded, and the button would

Facebook's drill button would be hidden in a huge list of other buttons, the order of which changes randomly every time the page is loaded, and the button would only show up 30% of the time based on an algorithm. Some users would never see the button based on what the algorithm decides, despite specifically adding the button to their list.