When using a curve as an animation path, an angle formed by a control point may or may not fall perfectly between curve segments. The angles may used to change direction of objects/cameras, usually with a stopping on the point and then starting up again in the new direction. If the control point does not occur between curve vertices, the animation path can't have a perfect angle and the result is a weird jittery motion right before the object "snaps" back onto its path. Increasing the curve resolution doesn't necessarily help because even at a resolution of 64, it may not be enough to give the illusion of a perfect angle.

This can be solved by allowing control points to fall directly on a curve vertex. That way, we don't have to interpolate relative to the arbitrary bezier control point and the angle can be perfect.

.blend attached that shows the problem.