Lightning
Lightning is one of nature's most powerful forces, and a raw example of electricity in action. This electrostatic discharge arcs between a cloud and the ground, a cloud and other clouds, or simply within a cloud itself. While lightning producing conditions can be predicted, even the National Oceanic and Atmospheric Administration admits there is debate on how precisely it is formed.
Computer Risk
According to the National Weather Service, using a computer during a lightning storm is a safety risk. Because a computer is often directly connected to electricity via its power cable and any associated internet cables, the computer has many avenues to transmit electricity. Laptop computers running on battery power and disconnected from any physical cables should still be safe to use, because they are disconnected from electrical power sources, and contrary to some myths, electricity cannot "jump" through radio waves being transmitted by a wireless connectivity device.
Other Electronic Risks
Many other electronic devices are a risk during thunderstorms. Corded telephones in particular prove to be a potential risk, with many injuries and fatalities attributed to lightning strike via telephone. Essentially, any corded electronic device or electrical appliance in your home can provide a point of electrical transmission as long as you are in contact with it. While wireless or cordless decides are essentially safe while indoors, using them outside during an electrical storm can carry a potential risk. Even something like an iPod can be a hazard outdoors.
Documented Cases
WCVB Boston reported the July 2008 case of 19-year old Anthony Tomasz. He had reportedly been sitting at his computer when a bolt of lightning struck his home, jolting electricity through his computer and sending Tomasz flying across the room. The teen's uncle, who found him only semi-conscious, stated that the lightning had traveled through the mouse and down to the bottom of his foot. In Vancouver, a 35-year old man was hospitalized in 2005 when he was struck by lightning while jogging listening to his iPod. The man sustained burns across his body consistent with the pattern of his headphones, suffered a fractured jaw and had both eardrums ruptured. Although the iPod itself was not deemed the reason for the strike, its conductive metal parts were determined to be a factor in his injuries.
Precautions
Preventing injury during lightning storms boils down primarily to issues of common sense. If a storm is in your area, it's best to avoid using the computer or telephone unless you are using cordless and wireless varieties of either. Stay inside a building with permanent plumbing and electrical fixtures. Maintain minimal contact with electrical devices that are connected to electrical sockets can reduce your risk of lightning strike, as can avoiding contact with water, windows, doors and concrete.