There's a bunch of good uses for them (but none that outweigh the privacy problems). For example when you look at someone you met before it can pop up info about them like their name, business relationship to you, topic interests you've talked about before, etc.
In the Organic Maps app just tap the button with 3 lines (≡) in the lower right corner, then tap "add place". To update info on a thing that already exists just tap on that thing and then tap "edit place" at the bottom of the page.
Orange is the visitor? His tail is poofed out