An amusing wifi story:
A buddy has his PC on wireless at his brothers house. Every time they turn on the dryer which is between the PC and the access point signal strength drops in half. I have him building a windsurfer wifi antenna.
The 0.72 is the overhead time that ethernet protocal uses to handshake the data connection.
Dividing by 8 is the conversion from mbps (megabits per second) to mBps (megabytes per second).
With 10 meg wired I hit the ideal number on my net. When I went to 100meg wired the speed did not make it all the way to the ideal butit was close.
From what I've read the overhead used by the wireless connection is a lot worse than the overhead of a wired ethernet lan. And low signal strength or electronic noise (motors, cell phones, portable phones, CB's, etc.) makes the overhead even higher.