As in all consumer products safety is a great concern. Safety for the user and others. Since toys involve children mostly, you would expect the designer to incorporate safety features especially when fast moving parts are involved. One classic example is the toy box, some have heavy lids and if there is no safety device to stop it from slamming and injury to a body part can occur. Both friction hinges and rotary viscous dampers can help with lids slamming down but I think rotary viscous dampers would be better  because a partially open lid would eventually close safely , not allowing babies or pets to get in and unable to exit. Its also a cleaner look if the lid was closed all the time.  A friction hinge would need a larger force to close which a child may not be able to exert, maybe even hurting themselves while closing it. contact us at www.mmtech.us for your next design project or call at 203-406-7900.