The WSJ has an article on light pollution: http://online.wsj.com/article/SB121692767218982013.html?mod=googlenews_wsj
Light pollution has tripled since 1970, according to Italian astronomer Fabio Falchi.
Not mentioned in the article is the billions of dollars this light represents in wasted energy costs in the U.S. Every business should be aware that some large percentage of their lighting bill goes out without making a cent for them if they aren't using fully shielded lights. Using those clichéd acorns to light your lot? You are losing some 70% of your electric bill for lighting straight into the sky and into the pained, scrunched, unhappy eyes of the customers who can't see beyond your lights, who can't see into otherwise well-lit areas in your lot because of the glare from the acorns.