There are many causes of nausea. Here are the environmental factors to consider:
- The larger the screen, the more likely to cause nausea.
- The closer the user is sitting to the screen, the more likely to cause nausea.
- The darker the room, the more likely to cause nausea.
- Third-party viewers -- non-interactive passengers -- are more likely to experience nausea than someone who has some form of control over the game.
- A slightly skewed viewing position will typically cause more nausea than a straight-on viewing position or a sharply skewed viewing position. (This typically interacts with #4, above, making things even worse for non-interactive viewers)
(You normally don't have control over these environmental factors, unless you're making a gaming installation. In which case, you absolutely should be considering them.)
Remember that nausea is caused by a disagreement between what's being seen by the eyes and what's being experienced by your body's internal motion sensors in the inner ears; the more context that your brain gets that motion being seen by the eyes is not an actual motion (say, by being in a well-lit room with plenty of stationary objects visible behind the screen), the less nausea will be experienced.
In terms of the camera behaviour itself, any sort of automatic rhythmic motion can easily cause nausea. Rotations are worst (particularly tilting), but even rhythmic translations from side to side or up and down will cause nausea for many (but not all!) players.
For this reason, if you use camera bob, it's important to always include an option to disable it. Otherwise, many players will be unable to play your game for more than a few minutes at a time.
As a rule of thumb, the slower the cycle and the smaller the motion of the camera along that cycle, the less nausea will be caused for the players who are susceptible to it.
Additionally, sudden changes in velocity are particularly bad for nausea; any rhythmic motion you choose to use should be smooth through its whole arc, rather than 'bouncing' along any axis, the way that your example graph does.
It's also worth noting that most players do not have nausea responses immediately; those responses build up over a few minutes duration. Some games therefore only perform these sorts of camera movements periodically; for example, when the player is performing a duration-limited "sprint" move, rather than all the time when the player is running normally. It's still probably important to allow those who are susceptible to nausea to disable the effect entirely, but more users will be able to tolerate the effect if it's infrequent than if it's constant.