A good ground connection is essential to the safe and reliable operation of any piece of electrical equipment in the home. Electrical grounding ensures that if there is ever a short on a piece of electrical equipment, current will flow through the ground system and trip a breaker or blow a fuse, thereby providing protection from injury or electrocution. Grounding also is the primary path through which a surge protector dissipates energy from an electrical spike.
A ground system's ability to dissipate electricity is measured in ohms. The NEC Article 250 calls for a ground system of 25 ohms or less with 0 ohms being the unattainable but theoretical "perfect ground". Properly installed ground rods achieve the 25-ohm requirement.
Equally important is that all wires and pipes entering the house be bonded to a single ground point. This means the electrical, cable TV, water and telephone phone systems should all be connected with electrical conductors.
Separate ground rods for phone or cable, that are not connected to the electrical ground rod, are unsafe and probably a violation of the local electrical code.
If you have a ground rod installed, be sure it tests to less than 25 ohms. If you have a ground rod and the cable or phone lines are not bonded to it, contact the appropriate utility and ask them to come check your system. In most locations, it is their responsibility.