No personal direct experience of dowsers but there is something in the back of my mind about James Randi being sceptical about their "powers".
That's whom I was thinking of with my "double blind test"
Randi offered $1 million to anyone who could prove they had paranormal ability. The way it worked it is they would come to him, and agree a test and then they'd do the test. As I recall, the dowsing test involved 3 buried pipes, with water running through one at any time. They agreed a criterium - how many attempts and how many of them had to be successful to prove dowsing. No one took the money.
It was a feature of Randi's tests that the applicants would protest the conditions were unfair after the test, even though they freely agreed to them before hand.
I notice that dowsing is more popular in countries with high rainfall, like the UK, where you are more likely to find water wherever you dig.
Anyone play with ouija boards as kids?