"Power line networking adapters are really nothing new. They have been in use in Europe and the Pacific for years. This is due mainly to the way buildings are constructed (and the large number of older stone and brick buildings) where you can end up with a large wireless dead zone in your own home. Enter the power line adapter. It can use the electrical circuits in your home to create a LAN connection. Power line adapters have been making their way over to the U.S. as well.
The adoption of power line has been slow in the U.S. mostly due to the wood and gypsum board construction in houses. There are still places where older steel and stone construction interferes with wireless signals and it is there that we see the most significant market. Power line adapters like the HP-3000E are also becoming popular with people concerned about wireless security."