Electronic Engineer here, specializing in static electricity and it's effects upon consumer goods.
1. A lightning strike within 5 miles, induces a voltage of 5,000 volts per meter of wire, in your Doorbell wiring, in your alarm wiring, your telephone wires, your AC electrical wiring, the coaxial cables (TV, Video, Broadband), and even across the cows front and back legs, (heart in-between!), that die in the field.
2. Just turning OFF any appliance isn't much protection, all wiring needs to be disconnected!
3. because #2 is so rediculous for most of us, with two or three TV sets, several video PVR/DVD/VHS items, Phones, computers that are networked, the solution is:
Tripp-lite, APC, or Belkin Uninterruptable Power Supplies, of 350 Watts to 1,000 Watts capacity. They contain surge suppression, PLUS, back up power for enough time to safely shutdown everything. I run twelve, in my home, in Central Florida, the Lightning Capital of the USA!
On sale, usually at the large office stores, and the warehouse clubs, for about $25.00 (for the 500VA=350 Watt unit at Office Max, this past weekend), and up (1,000VA for $89.99 at Costco, this week).
The only thing NOT protected after that, is the phones, coaxial TV and Broadband cables, and the ethernet cables. The answer is to purchase a special surge protector for each of those. For the ethernet, there is the UPC "ProtectNet" "PNET1".
The majority of computer failures from stray energy in my MacIntosh repair shop, are due to the Ethernet getting high induced voltages... and, most are on the Main Logic Board, which ends up in the replacement of the most expensive part of any computer!
The OTHER extreme failure is in the phone modem! My lines plug into a properly grounded Surge Suppressor that has phone jacks, Cable TV coaxial jacks, and the standard AC outlets, with an insurance policy of $30,000.00! Sold at most major retailers, like Wal Mart, Target, K-Mart...