For anyone interested in this topic. I found this excellent explanation in Google's handling of redirects since the Bigdaddy update on Matt Cutt's blog. http://www.mattcutts.com/blog/seo-advice-discussing-302-redirects/ And 'seo black & white' responded in the comments how this exact situation is a flaw in the system "I see a possible problem with 302 on-site redirect. This is the case when the site we’re speaking about is some freehost (say somefreehost.com). It is not a secret that subdomains/subpages of such sites often used as doorway pages (say somefreehost.com/guestbook/trampoline-to-be-positioned-for-phentermine-keyword ) by black hat guys/girls who create many spammy backlinks pointing to it (for positioning them). Once discovered by freehost owner these pages are often deleted by putting 302 redirect (to the main page of the somefreehost.com) just because this is a standart rule for many free hosts - 302 redirect from any non-existant page to the main page. After that all of us will see somefreehost.com on the 1st SERP for `phentermine’ for weeks. It have hapened many times in the last half of the year (I had not monitored SERPs before that."
This is a very common BH technique. Exploiting scripts to create dynamic pages with the link you want on it. What I don't understand though is why someone would want Keycontent to rank for Viagra, surely that's a complete waste of time. They would be better off putting their resources into a Viagra site
Well the goal is simply to get ANY page to rank for the terms they are tagetting and have that page redirect customers to the target monetized pages. User searches for viagra, clicks away on the top 5 listings, hits the redirect page and bam, they are at the target page. BH profits using whatever monetization scheme they have available. The more rankings the better. If they just spammed their target page, hosted on some throw away domain it would last a week or so and be gone. But by proxying through other's domains, the rankings achieved have the potential to last a bit longer, also it doesn't matter if their target domain is banned from the indexes as they are ranking established sites pages. Now if you were refering to the practice of using dynamic pages ONLY for an extra link to the target site and not actually redirecting then it would be excessive to rank the "victim" for this. Some will still do that to try and bump the PR/Authority of the generated page a bit and increase it's supposed linking value. Definatley debatable whether it would be worth the effort.
Well the reason they use a "mature" domain is because it will be MUCH easier to rank than a new one with Google. If I threw up a new site and then pointed lots of links at it it would trigger a filter at Google (the BLOOP filter) and would be sandboxed\penalised. If its a mature site and trusted then it would rank very well... My 2 cents.