Google is paid to ensure some websites end up at the top of a search.
Somebody has probably figured out how to use a bot to put their particular website on top.
By using that filter, they are ensuring whomever is doing the searching is actually human.
Got a link for that?
I've got a web site that isn't taking off. Sounds like you've got the solution! Where do I click? How many hits do I get per dollar?
Just ask Ricky about that. Converted his name to a common noun! LOL!
Of course, that feat was not accomplished by paying Google. Rather, it was by fooling Google's search algorithm. This is confirmed by the fact that non-Google searches also uncover the disgusting substance high in their SERPs. From Google's point of view, this is a bug, not a feature. And certainly not a feature Dan Savage would have had the funds to buy!