Man, some of you folks are SO freakin' negative!! This could be an opportunity to show detectorists as stewards of the environment- folks who respect the land, remove trash they find, and recover artifacts (and art) to later be shared with the public once more. Not to mention those MD'ers who recover engagement rings, wedding bands, etc. for silly folks who lose them.
Of course you couldn't characterize the hobby as a "thrill a minute" endevour. But not much of life is constant thrills. Show it for what it is- lots of hard work for little, or no, payoff. When folks see that it's not as simple as** 1.) buy detector 2.) go waddle around the yard for a few minutes 3.) find treasure chest! Now I'm rich!! **they leap off the couch and clean out your favorite honeyholes, leaving candy wrappers and soda cans in their wake.
Go ahead, someone slam me for having no experience in the hobby. However, I have learned enough about MD'ing to realize that there are great hobbyists out there, who could make this project a really great thing.