I remember reading this article a month ago about Shell pulling out of a wind power array project.
http://www.theregister.co.uk/2008/05/01/london_array_shell_pullout/
It got me to thinking about how big would an array have to be to power the US.
That array would produce 1,097 GWh per year on average when completed and takes up 94.6 sqmi.
The US consumed 4,053,000 GWh in 2006
If we build an array to supply all of the current US electrical
needs, it would take up all of Texas and New Mexico. It would be a total of 1 million wind turbines.
edited: wrong/mismatched calculations from a reference site on Earths size caused me to get some strange results and I ran with them before checking them.