Although it would allow for uninterrupted communication and observation of the Martian surface, no artificial satellites have been placed in this orbit due to the technical complexity of achieving and maintaining one.
Mars's gravity is also much less spherical than earth due to uneven volcanism (i.e. Olympus Mons).
This creates additional gravitational disturbances not present on earth, further destabilizing the orbit.
Solar radiation pressure and sun-based perturbations are also present, as with an earth-based geostationary orbit.
Actually placing a satellite into such an orbit is further complicated by the distance from earth and related challenges shared by any attempted Mars mission.
[2][6][7] Satellites in an areostationary orbit would allow for greater amounts of data to be relayed back from the Martian surface easier than by using current methods.