Long a darling of the online porn biz, the practice of creating dozens of mini-sites to link to the main one has been valued as a great Google-snare to direct traffic to the ‘mothership’ site.
It may fool a search engine into thinking that the ‘mother ship’ is hugely popular. But the search engine then looks to see who is pointing at the fake sites. Of course, the linkage surrounding the fake sites will be very weak and based on mainly inbound links from the same network. Basically, it is a spam island, pretty much isolated from the rest of the community. That’s not natural, so it will likely get penalized.