Why is the first tag sometimes in the <title> tag of some questions?

Question

I searched through Meta and couldn't find an answer to this. I was reviewing my questions this morning and I noticed that in certain questions like What is the effect of falling to your death in Metroid Prime 3, the <title> tag on that page shows:

metroid prime corruption - What is the effect of falling to your death in Metroid Prime 3? - Gaming - Stack Exchange

So it's like the first tag (s/-/ /g) is prepended to the question title to make up the <title> tag. Why is this? Because it happens here also, and on meta, but it does not happen always.

What is causing this behavior and where can I read more about it? (Or should I ask on Mother Meta?)

EDIT: Now with Freehand Circles:

Answer 1

At Grace Note's suggestion I want ahead and asked on the mother of all meta sites where a friendly gal named Rebecca gave me a nearly instant answer. I'll update this answer as more appear.

In order to try and stop the scrapers from being ranked higher on Google, they are working on increasing their SEO. To this end, the tag listed first on a question (sorted by popularity of the tag) will now appear at the start of the page title. Search engines like having keywords in the page title, specifically at the beginning of the page title. If the tag is already in the title, then this new approach won't duplicate the keyword, as you've noticed with several of your links.

I've asked a related question about the ordering of keywords on Webmasters.

Also, Benjamin Dumke, (Stack Overflow Valued Associate #00007, better known as balpha ♦ or Lord of the Chats) confirmed this and offered more explanation:

"seems like if the tag is already in the title, it won't duplicate it" -- that's correct. – balpha♦