Why can't electrostatic forces "pierce" through thin obstacles the way magnetic forces do? We know that two magnets attract or repel each other even when we keep a very thin obstacle between them such as paper. Why doesn't the same hold good for two charged objects?
 A: The implied assertion that magnetostatic fields can penetrate thin layers better than electrostatic ones does have some truth to it and the reason is that there is no free magnetic charge, whereas matter is electrically charged. If a material is conductive, electric charge migrates until there is no force on it, or until all forces are balanced. That is, charges arrange themselves to annul the electric field inside the body of a conductor, otherwise the conduction charge inside would keep moving under the influence of the electric field until there were no electric field there. Electric field lines enter conductors normal to the conductor's surface for the same reason - charges rearrange themselves until the forces on them are normal to the interface between the conductor and the outside World, otherwise the charges keep moving along the conductor under the influence of any tangential electric field until the latter is annulled.
Therefore, many materials exclude electric fields. Magnetically shielding materials also exist, but these work by a wholly different principle. Hollow mu-metal shields (such as those used around cathode ray oscilloscopes) exclude magnetic fields from the hollow by providing a low magnetic reluctance path along the shield and around the hollow. This happens simply because the mu metal has an enormous relative permeability - typically approaching $10^5$.
