This is the latest from a desperate Google. Why is Google desperate? Virtually all their money is being made via ads, their original business plan. Asteroid mining and other BS "We're curing death" press releases aside, Google is dependent on adwords so they need to keep turning knobs to force sites to advertise. Their PE is 25+ so they need to show huge increase quarter to quarter to keep the scheme going.
This month Google also made the Keyword Tool for advertisers only. And in another major coincidence after Page took over, Google has made major algo changes (Panda, Penguin) giving sites virtually no way to come back in ranking but that greatly improved Google's revenue. Shocking, huh? Of course they can advertise to make up for the lost traffic, like the sites that rank high (brands.)
So do I have a smoking gun memo? Nope, but it doesn't take a genius to figure it out. Ever wondered why Wikipedia ranks #1 for "computer"? IMO, it has to do with forcing Dell, MS, HP and others to advertise and to increase clicks on ads. I doubt most people want to know what a "computer" is when searching Google on a computer.
That Gmail "promotions tab"? Google attacking another free source of sales and marketing.
P.S. I expect a gazillion down votes from you know who. I don't care.