walkman - 5:56 pm on Sep 17, 2011 (gmt 0)
My guess: G cannot legally do what has been doing lately, filling the top with G+ for legal and PR issues. So they will use the excuse of 'social' and include some non G+ too. Of course the deck will be stacked but it will seem a bit better, considering how everything Google now does will be scrutinized by the frogs in pot of boiling water.
I think it's a test of some new idea - and no, for the search where I saw it, I did not find all those tweets useful.
If they cared about non G+ social they would have renewed the Twitter deal, especially since they are frozen out of FB. Twitter wanted to charge them tens of millions a year, IIRC. That's peanuts for Google so it isn't the money but the desire to promote G+ and hurt Twitter at the same time. Follow their long term goals of dominating and short term %$$ goals and you have the answer to almost everything Google related