I don't have examples that I could share in a QA Forum, but think from Google's Webspam team perspective. Artificial SERP manipluation in indeed a big problem for them. Think about the Whitehouse Google Bomb (Bush's Miserable Failure Search). It's just too easy to detect and not worth the risk. It all depends site to site, depending upon a site's link profile history and age.

In my opinion and a test I conducted last year, the plural worked out to be better. Again, the test was not a 100% apples to apples comparison.

I registered 2 domains one singular and the other plural on different registrars. Hosted them on different servers. Got 5 articles written for each site (and that is where it starts getting different), since I am not using the exact same articles on both domains, I am sure this also factored in. In my test, the plural ranked much better in the SERPS not just for the head keyword, but a lot of variations/long tail keywords. The singular one also ranked, but for a lot less keywords.

I would do the plural any-day unless it's a niche where plural sounds weird. I hope that makes sense and helps. SEO History in your example makes it a much better and easier decision.

I am presuming all those domains are linking to each other, correct ?

Are they regular or nofollow links ? It boils down how much authority you have on your main domain as well as the other domains. If I were you, I will keep the main e-commerce website on one server and everything else including niche blogs etc on a different server. It's not just SEO, but also security issues.

Essentially, to answer your question, it may not be hurting you to have the niche blogs, a forum with user generated content, the articles site and the corporate site on the same IP/server, but it would help you a lot more if they were on a different server, possibly different Class C IPs. So, you will gain from these links being on a different server. Keep in mind, these links are important for you and its good to increase their value by hosting them separately, because these sites are links that your competition can never get linked from. I would also consider doing a nofollow on them, and that's just my thoughts. I prefer lower risk. Again, it depends on what your e-commerce website's link profile is.

I agree with Marek. However, there's value in having the Category in there specially if your categories are keyword rich. Don't worry about duplicate pages. One post will only have one default category in the Slug (Most of the times, its the 1st one you selected in Wordpress). I also sometimes like to use /%category%/%postname%.html or /%category%/%postname%.php which gives the effect of pages under a folder, vs folder inside a folder. Just my 2c.

Based on my experience and a look of your site, I am inclined to believe that your local / GEO keywords associated rankings might not get impacted as much if you get rid of it from the Page titles. Test it on some pages and use more important/low hanging fruit/long tail relevant keywords and see what that does. Test it on maybe 10-20 of your pages which do not get any GEO traffic, but rank for non-geo keywords and see if those pages can rank for 1-2 additional keywords.

Great response Nicholas. @AWCthreads, Do you have your city/station in the footer ? How many pages do you have in your site ? Do all of them have City/State targeting in them via Page Titles ? Do all of them get traffic from keywords with Geo data attached ? Does your website have a Regional Dmoz listing ?

It would not be a good idea to interlink them for SEO reasons as you mention "creating a link wheel/pyramid". I would ask these questions to myself: 1. Do all the sites have unique content ? 2. Do they have any duplicate/repurposed content at all between theme ? 3. Do uses on one website need to navigate to the other website, since it provides value to the user ? 4. Have you considered nofollow links ? This is a bigger strategy discussion that you have to do to figure out your next steps. If they don't provide too much of a value, how about you aggrgate the content on 1, maybe 2 or 3 combined sites instead of 50 and 301 the rest ? It's really difficult to answer further without knowing more in detail. I hope this atleast invokes some questions and a long term SEO strategy.

I agree, this is not automated but so far, from what we know, looks like a nice and clean option. Thanks.