LOL . . . Just read the thread and see others had the same idea . . . Sorry, when out for lunch and when I came back and saw your post, I wanted to responds asap so you wouldn't think I was one of those hit and run posters! :-)
Regarding your point about not being able to catch everybody -- or maybe not even being able to catch one person -- it's sort of like laying mines: You make everybody behave and be cautious, including the minority who are doing this stuff.
I live in Nashville--home of the Ultra-liberal Davis-Kidd stores. When I went to purchase Unfit for my 12-year-old (his request!!), they had it buried in the back and at full price (no "bestseller discount")....When I saw Molly Ivins rag with the discount, I decided to take my money elsewhere. I ended up buying the book at Borders for 30% off retail from a snarky Vanderbilt goth-wanna-be. I would have preferred to buy it from someone who would be as excited as I am that my pre-teenager is interested in this type of reading....but that's part of my utopian dream. ;)