I don't think a lot of what you are referring to are actual sites. There are a lot of addresses, and a lot of webpages, but not a lot of genuine sites.

You can buy a domain name at godaddy for a few bucks, put up a single full page ad for a sponsor site, slam a million reciprocals on the bottom of it, do a little SEO and VOILA'.. you have a presence on the net. Then create sub pages, do the same thing, different sponsor, and VOILA' you are a porn baron on the net. You never have to buy content, you never have to deal with customer service, you never have to design or create anything.

Look at most of the "sites" on link lists, top lists, etc. and they are mostly nothing more than TGP gallery pages with sponsor banners.

THAT is what there is too much of. IMHO