It's interesting the bulk of the replies have railed on the OP for not being more adept at using their main map to find other players and also on the exact content of the example they used when, in my opinion, that's an insignificant sideshow.

The real value in pinging your map lies in telling people where to go to meet you or where they should go to find something you've directed them to, not necessarily them finding you or you finding them. For example, "Go to the spot with the stuff."; "What are you talking about? I have a bad sense of direction..." "*PING*" "Oh there. thanks". A ping is worth 1000 words, or if not 1000 then maybe like 40 or 50.

On a semi-unrelated tangent, add the ability to mark up your own main map with points of interest and maybe even some notes.