This page is meant to be included in various places.
Why I would invest in Oasis if I was Wikia Edit
I am not Wikia; I'm not employed by them and have no inside knowledge. However, I have wondered why Wikia has invested considerable resources into their new skin project. When asked, "why the new skin", the answer is usually some vague waffling about user experience and moving with the times. If I was Wikia, I'd invest in a change like that for my bottom line. Here's how the most marked changes affect it.
Behaviour tracking boosts ad sales Edit
Targetted advertisements can be sold for twice as much as normal ads. Wikia hides most tools in dropdowns; the ones still in the open are "share" and "follow"; both indicate what a user likes, and some ad networks are able to track clicks to these links and correlate them with page content to get a picture of the reader's interests. ("Google also plans to go head-to-head with Facebook's "Like" button—a tiny tool on many websites that lets people tell friends they "like" something. Each click gives Facebook valuable, personal data about people's interests."  ) An added benefit might be that the "cleaner" page helps behaviour analysis algorithms to more easily filter out unimportant clicks.
Wikia have already told us they do click-tracking -- usually in the context of "studies". With the topbar, they have a way to centrally present some interests that advertisers may be interested in - and every time your mouse moves from your browser toolbar to the wiki toolbar at the bottom, one of those things pops open. If I was Wikia, I'd definitely cash in on that.
Some anonymous editors felt forced by the new skin to create accounts for themselves so they could access RecentChanges etc. since anons do not have access to a toolbar. Logging in is one more way of reliably tracking users, and it increases Wikia's "subscriber base", making the site seem larger to advertisers.
Increase time spent on Wikia Edit
The "Wikia rail" at the top might help people who get bored with one Wiki to stay longer on Wikia, exploring other wikis. This increases a metric that is important for advertisers: the time spent on the site (site being Wikia). It makes Wikia appear more attractive to users, and allows it to serve more page views and helps sell ads.
Remove in-content ads Edit
Advertisers demand the box ad in the upper right corner; on the other hand, it is possible that Wikia research found that in-content ads are now less effective than they were thought to be when introduced. Integrating the box ad in a right sidebar solves this. ( somethingawful.com had this 2 years ago! )
Update: Wikia is now using the "empty space" in the lower portion of the sidebar on long pages for ads as well. (Source: User blog:Ciencia Al Poder/December update - New ad formats for your visitors)
Provide a new ad location in the margins Edit
Other sites already use the margins to display advertising (Keenspot, a webcomics site, already does; webcomics have a fixed width anyway). 
Update: Wikia is doing it, too, see screenshot.
I'd put everything that's personalized into widgets that get loaded via Ajax; that way, I could cache the same version of any page for everyone and let the browser create the personal links and load the personal tools separately (only one load for each user, from then on out it's in the browser cache). Normal Widgets such as the shoutbox would have to go; they can't be cached as part of the page.
It seems that despite "hiding" the personal stuff, Wikia isn't doing it that way (yet), with the personalization still being provided by the server as part of the page.