As for adult VS mainstream, here's a quote on Threadwatch by Mr. Turner (whoever he is) in response to Matt Cutts admitting Google cannot tell the difference between a quality porn site and porn spam:
Quote:
To understand why the results are poor in adult, you have to understand how adult sites work. You essentially have under 1% of the sites that actually sell something, and over 99% of the sites pushing traffic to those sites as affiliates. There is very little middle ground here. You have very few sites that put up porn for the fun of it. It’s essentially like taking a mainstream industry and dropping every site in it that doesn’t sell something or is an affiliate for someone.
So what that leaves is a group of webmasters all fighting for the same dollar. No one is giving up links to other affiliate sites because they feel it is beneficial to their user. No one is linking to adult sites just for the hell of it as well. The primary way of getting links has been through trades. While this was fine and dandy in the past, as Google’s algorithm advanced to spot link schemes, adult has been sacrificed because of it. Since most sites have relied on reciprocal link trading and since the industry lacks any natural linking because of its nature, it simply doesn’t work in an algorithm geared toward mainstream sites.
So what you’re seeing is sites that were popular in the past become untrusted, which in turn flourishes to new sites that receive links from them. A lack of “trusted” and “authority” sites has made it difficult for new sites to flourish as well.
To me, it’s not about Google blocking out adult content. Heck, a good percent of their searches are adult oriented and there are certainly better ways to block out that content than this. I think it’s just a case of adult having a completely different structure than most mainstream industries.
|
Here's an unfounded theory for thought:
If Google is using a variation of the TrustRank algorithm, then Google cannot tell the difference between low PageRank quality pages and low PageRank spam. Because most links on adult sites are devalued due to lack of trust, average TBPR in adult compared to mainstream is low. Specifically, I don't know any adult sites with a TBPR 9. Even if low TBPR has no impact on rankings, it means that you'll see more spam on adult SERPS than in mainstream. It also means adult sites have a bigger tendency to lose rankings or go supplemental.