Also I think it can happen for if someone dies that they go into spectator mode. While this happens, if they fly in front of you directly, you can see their name. Sorry for double post ;)
this old glitch appeared ever since v21 was released at some point of time in 10th of august 2012
i dont know how to replicate this glitch but ive seen it in action, its completely harmless but you gain the ability to see the spectator's name tag on their 'head'... so all you get is to know the spectators name and thats it, no gain other than knowing him/her looking around
completely not hacking its just an old glitch ( cant confirm if it had existed in v20 and back but im sure it didnt ), so if your quite paranoid if this might destroy or cause any problems calm down its not going to
conclusion: drydess just encountered a glitch and you kind of overreacted