Looking at the history that Nik has, as well as the other products they acquired, it seems like photo editing in general was the target. Something to make Picasa a (hopefully) better product in the long run.
Picasa is like the Google+ of social networks, it had some loyal users who want it to be the next big thing. But that won't happen any time soon. Google will invest in this niché premium market for tablets. With the incoming Nexus Phablet and November's rumoured 10" tablet, they'll try and prove that Android offers more than casual/convenient usage.
I know Snapseed is popular, but I think Nik is actually more known for their other products, at least with photographers.
Silver Efex is easily one of the best black and white image processing tools around.
In Nik Software's case, it feels like the acquisition was a good balance between acquiring a team and acquiring patented technologies (http://www.google.com/search?tbo=p&tbm=pts&hl=en&...).
You can see the interface in action on their website. Load the following link (http://www.niksoftware.com/colorefexpro/usa/index.php?view=h...) and then click on "Working with control points". It's in an embedded flash player so I can't give a direct link.
Google -- if you let Nik's "non-sexy" non-mobile plugins for Photoshop/Lightroom, etc die on the vine I will never forgive you. Either commit to them or sell them off to someone who will keep them maintained.
My Google+ feed is way more useful to me. I follow a lot of fellow developers & tech personalities who post long-form content that can't fit on Twitter.
My Facebook feed has too much personal/trivial posts that I value it less. Not to mention the endless political rant.
I actually think that Facebook & Google+ comparison is not right.
The people I follow on Google+ are more similar to the people I follow on Twitter. But Google+ has an advantage because it has no 140-character restriction & displays media (video/picture) better.
This (acquihire? patent-grab?) is a gut-punch to photographers, if nothing else.