It helps to know a fetish well enough to recognize the places where personal fetish maps commonly overlap.
Fer instance, a foot fetishist is often also a leg man, and sometimes an ass man -- but rarely gets more excited than normal by boobs.
The genius of the
Tusy Cash sites is a result of understanding the overlapping fetish maps. They have spanking site that also toys with age play and anal stuff (rectal temp taking etc) which are fetishes that often overlap with spanking. Then they have a medical anal fetish site that does the temp taking plus enema stuff, which is another frequent overlap with spanking fetishists and with guys who are turned on by asses.
I'm not saying they always get the mappings exactly right, or even right for the majority of surfers -- but their sites are clearly inforrmed by an awareness of the way in which various fetishes overlap, which puts them light-years ahead of the cookie-cutter people.