Just to put a spanner in the works - we have recently changed over from Wireless to Homeplug - which used your electricity copper ringmain as a computer network
Our house was built in the 50's, so all the internal walls are brick, and the Wireless network just didn't work between rooms/floors reliably
We have one Homeplug terminus that takes the input from broadband, and then each computer we want to attach to the network has a Homeplug unit plugged in nearby, and a standard network cable attaches the computer to the network. If you want to move around, it's not a big problem, as it works over extention cables, so I can still surf the web on my laptop from the garden
It is more secure than Wireless too - there have been recent court cases of people sat in cars outside peoples houses using their wireless network to access the internet and get up to no good; and it can be difficult to prove it was not the householder
Wireless networks
can be secured effectively, but a lot of people don't bother or don't know how