In the bigger picture, people were starting to catch on to the fact that Google's search product was becoming increasingly useless.
Around here we'd come to that conclusion at least a couple of years ago, due to abusive SEO and so forth. And that understanding was becoming even more widespread.
I don't know if Google's got the later parts of the game figured out yet, but I have to think that they'd realized that Search was dying. While there's still some value there, may as well use it as a hook to pull people into what they expect to be the next era.