Google's new Google Trends service provides information on how frequently different terms have been searched. Interestingly, it seems that the volume of searches on "polygraph" is lower in 2006 than it was in 2004:

http://www.google.com/trends?q=polygraph

Also, for reasons that I find baffling, the #1 region from which "polygraph" is searched is -- far and away -- Sacramento, California. Numbers 2 & 3, Reston, Virginia and Washington, DC are more readily understandable. :)

It also appears that searches on "lie detector" have fallen off since 2004:

http://www.google.com/trends?q=lie+detector&ctab=0&geo=all&date=all

Again, the #1 region searching for "lie detector" is Sacramento.