As Robin Whittleton correctly pointed out, MOSJÖ does not need to be anchored to walls, there's no such instruction in the manual and there are no anchoring parts provided.
Considering we're on Home Improvement site, you can add doors, shelves etc. to it on your own. From now on true common sense must work.
There are two modes of failure of the furniture one must take care of. It can either collapse unter the load or it can flip over. Anchoring addresses the second option.
Old furniture used to address the flipping by using heavy frame structure, light doors and few drawers close to floor. Those wont flip because the centre of mass is always in the furniture.
Younger pieces were proteced by screwing together building one big solid body that is heavy enough to be flipped easily.
New pieces are "design" and optimized for price. The result is lighter body structure and heavier doors, taller drawers etc. Glass, which is much heavier than wood, is used more and more. Such pieces must be anchored because even opening door or drawer can move the centre of mass too forward to flip it over.
Another point of view is stability of the whole setup. Older equpment is either smaller or heavier than today's equipment. TV sets were more like boxes (with all three dimensions simillar), new LCD/OLED/plasma screens are more like sheets (one dimension negligible to the other two). Speakers were rather heavy wooden boxes, now they are "design" tall tubes, shells etc.
Now imagine something hitting the MOSJÖ with 20" TV screen on it. It is light, so is the screen so the supports will skid slightly which will put the screen out of ballance, which is, unlike the MOSJÖ, thin and tall...
So, the answer is: "No, you don't need to secure IKEA TV stand to the wall" but if you do secure it properly, the security gain overcome the drawbacks with high margin.