Although map hack is a seriues issue when playing online.
So just report those ppl and get them banned :P
Done correctly, a map hack is virtually impossible to detect. Even if you do have an inkling that your opponent is map hacking, it's difficult to actually prove anything. After all, just because someone seemed
to have the clairvoyance to predict your actions and outmaneuver you, it could have been a stroke of luck or an educated guess.