Sorry for the late reply guys, we're going to improve the wording around some of the settings in a future iteration of notifications. The "Social Interaction from other users" currently controls two types of notification - friend requests and notifications regarding users tracking you or your content. However, we've since temporarily disable the notifications around tracking until we refine the settings a bit more. So basically, at the moment it's only friend requests. There are currently no notifications related to endorsements or un-tracking. In the initial launch article I did ask if anyone had any new types of notification they'd like to see, but I didn't really get any feedback around that.