Google does not want to test caffeine on people like us, they want to test caffeine on what they consider to be the average searcher.
Right, which implies they are purposely trying to "hide" something.
My massively huge ego :) would love to say, it's simply because they don't want people like us announcing to the world, when they fudge it up, and the hows and whys, but it's gotta be something more than that, right?
Did they sneak the spyware back in, just less detectable? (not that many people noticed the first time)
Just thinking outloud this post, but continue to keep an eye on how they roll this out.
Those "other factors" usually make themselves apparent sooner or later and can be used for SEO analysis or simply catching Gorg trying to carve out their "Big brother" empire.