Our own ad server allows us to target individual countries and set times within those countries when ads should appear. I've got two campaigns set up currently doing just that.
Does that mean you change them for the "I've had a few beers and my credit card is here" time of day??
Sometimes I wonder if people here have been on any other commercial websites recently, the STW ads are fairly tame, on a par with the BBC from abroad. (I occasionally see some when I have to relogin)
In the end I pay for 3 sites (here, vimeo & flickr) as they give me something in return. I even get a magazine posted across the world with STW)