User blog comment:Rupert Giles/Global Navigation January Update/@comment-4899461-20150202232851/@comment-24025240-20150203180518

For a great many of our users they arrive at an individual community via external search. A week later they might arrive at a totally different community via search. The global nav is meant to unify those communities under one umbrella through consistent theming.

In addition, we are still aiming to have an improved global search that allows users to find any piece of content in the network from any page. Ideally this kid of experience makes everyone's community better by not having it so siloed from the rest of the site. But an actual global search is better understood with a consistent global element (think searching on Youtube, Facebook, Amazon, etc.)

But with all of that said we heard everyone's feedback about theming. And we knew that a large, Wikia-branded element that followed users down the page felt really intrusive to the experience. So we had to find a solid compromise and that's how we arrived at the scrolling transparancy.