Personally, I can see the "head-up" from a teammate IF they're actually playing. Specing the other team and reporting their position every second, is nearly a workaround for tracking a player (multiple players, same IP.... Fun if it really is multiple players on the same IP, but not so if one is the player, and others are just that player's eyes.
Sad thing is, how to tell the difference. The average player can't... so it's hard for them to find a cheat... not as easy even for a 1up who has access to player IPs, as they can't tell for sure, as (best as I know) there's no way to spec a spectator to see if they're just parked, specing and recording, or specing to give away position. To stop the specing makes it easier for a hacker to cheat, which is even worse. It's a mixed bag, but unless you limit concurrent connections per IP address (not good if you have friends, family, or a spouse who likes to play with or against you on the same server)... no easy solution, and unless you want to be as popular as SCOTUS is right now... probably best left as-is.