Although smart fluids are rightly seen as having many potential applications, they are limited in commercial feasibility for the following reasons:
* High density, due to presence of iron, makes them heavy. However, operating volumes are small, so while this is a problem, it is not insurmountable.
* High-quality fluids are expensive.
* Fluids are subject to thickening after prolonged use and need replacing.
* Settling of Ferro-particles can be a problem for some applications.
* Cannot operate at extremely High/Low temperatures
Commercial applications do exist, as mentioned, but will continue to be few until these problems (particularly cost) are overcome.