I think it's an interesting choice to go dark. Regardless of what prior debates were had on this thread with respect to the "flat design" choice / minimalism there are two things that stand out.
1) It's original. At least, it seems original relative to its competitors. They are borrowing the well-accepted design language of their Weather app (which was critically acclaimed in relevant circles, I believe - like won some kind of award), and assimilated it across their web properties.
Contrary to what other's have said, I don't find the text hard to read. Instead, due to the novelty and aesthetic of the design, I am drawn to stay. It's a nice refresh.
2) It's cohesive. This design language has been consistently ported across its properties without making it constricting. Yahoo Sports is functionally distinct from Yahoo Movies, but blended together by the same aesthetic.
This began with Yahoo silently porting its top bar across its properties (with the search feature ubiquitous across all constituent sites). This final piece was missing and is just another step closer to bringing Yahoo together.
So no, I don't think the designs are cluttered, or that they hide/confuse information, or that Yahoo is copying the fad. I think they are paving their path, boldly, and it should yield some interesting results.