Disadvantages:

NURBS have several disadvantages:

• Extra storage is required to define traditional curves and surfaces, for instance, to represent the full circle by using a circumscribing square requires seven control points and 10 knots. Traditional representation needs the centre, the radius, and the normal vector to the plane of the circle. In 3D, this amounts to storing 38 rather than seven numbers.
• Improper application of the weights may result in an extremely bad parameterization, which may destroy subsequent surface constructions.
• Some interrogation techniques work better along with traditional forms than with NURBS. An instance is surface/surface intersection, where it is specifically difficult to handle the "just touch" or "overlap" cases.
• Fundamental algorithms, such like inverse point mapping, are subject to numerical instability.
• Before you begin feeling discouraged about NURBS, let us say that the above problems are not peculiar to NURBS. Other free-form schemes, such as those of Bezier, Coons, & Gordon, exhibit the same problems.