I have three of them. There's not enough yet. They don't work. Smarty-pants marketers stuff them with spam to send unsuspecting neophytes to their gambling or nudie site. Search engines take too long too.
Boolean logic has a long way to go.
It's a cool idea that hasn't quite been implemented properly. Most folks need to hit seven to ten sites before they get what they were looking for. If they're lucky. Soon someone will access its power but it hasn't happened yet. The study found that on average it takes 6 months to be indexed by a search engine.