Motion Sickness was first experienced by Pilots when Fliight Simulators where introduced for training, They called it Simulator Sickness.
It is related to travel sickness and it is caused by the brain which gets contrary signals from the senses.
The Eyes give the Brain the Signal "We are standing still", while the sense of balance tells the brain "We are moving" or vice versa.
Good examples are
Reading a book in a car - The Eyes are fixing on one point while the body notices the movement. That causes contrary signals resulting in Travel Sickness.
Another good example is Sea Sickness - another form - a boat or ship lies seldom absolutely even in the sea. The Waves keep it moving from one side to another (don´t know how its called in Englisch, in German its called "Rolling") and from Bow to Stern ("Stamping")
Those movements can be very subtile. While the Eyes tell the brain "Ship lies quiet in the sea" the sensitive sense of balance notices the movement and tells the Brain "We are moving".
Motion Sickness is the opposite, but works exactly the same way. You are sitting still while playing and the sense of balance tells the brain "We are sitting" but the eyes tell the Brain "Hey, we are moving"
Such things like "Head Bobbing" or "Movement shaking" (like in Mass Effect) makes it far worse.
The results are the same - dizzyness, nausea. I stopped playing in the past before it could get worse but I know some people which played until vomiting or collapsing on the floor, feeling like highly drunk.
It differs from Person to Person - the levels of what you can take or what makes you ill and how fast is individual.
Scientists started studys only a couple of years ago, when Motion Sickness in Games - Gaming Sickness - started to grow. According to these studys the brain starts to produce huge amount of stress related hormons - like in dangerous or life-threatening situations - which the body can´t handle.
I first experienced motion sickness when I replaced my CRT to LCD Monitors almost 10 Years ago. Before that Day I was playing a lot of Quake, Doom usw. Without Problems. But with C&C Renegade I got my first Problems. Some People blame the growing realism of Video Games for Gaming Sickness and it seems that Resolution, Monitorfrequency and the Quality/Sharpness of Textures have effect. Also the FOV. Some People claim it gets worse below 80° an gets better when its increased.
Edit:
For DAI it was enough to move the Camera out a littlebit more, like a MMO-Style Camera as shown in one Sceenshot above. A simple thing, which Bioware was not able to build into the game yet. Thats why I am really angry about them.
Delivers an awesome game - not able or willing to let the Player zoom out a littlebit more.