The game takes some time to scan for pivots. Each pivot you find is a cheat for the Animus. The pivot locations aren't shown on your map, you need to determine them yourself. You do this by placing pivots in the map: the lines drawn between several pivots will divide the map and show you where a certain pivot is hidden. Place another pivot as you get closer, until you have only a small section of land to cover. Once you're close enough, the Pivot shows up on your minimap. I dunno if they're randomly hidden or if they, as you say, are based on what other players do, but they're not really hard to find.
