I think fans can be made to rotate in both ways.The motors used for home fans use are generally single phase motors.They cant start on their own but can sustain motion when started, but you switch on the fan and it starts.The reason is....the  condenser gives a starting torque in that direction and the fan motor just sustains the motion in that direction.So next time when u start it before switching it on remove the condensor and then switch it on.It wont start now, with ur hands give it a push in the desired direction, hopefully if u havent made the ckt open it will start in desired diretion.When it comes to table fan, if u change the direction of blades..its acts like a exaust fan.Tables fans are invented first before celing fans.May be their blades made to rotate in anticlock wise.

me an electrical engg student, me too still dont have much idea on this.

may be u have to ask any professer who is master in elctricals r any electrician who has any idea on this.