Pretty sure they could develop chips with 100th/s capability, and run entire server farms of it. They make too much damn money the way it is.
This. The first part is because mining with CPUs and even GPUs just isn't (very) profitable. While Google only has CPUs (in great numbers - they do have other hardware, but those have specific tasks), consider Hollywood: a few dozen companies with more GPU power than any one entity should be comfortable with, accelerating computation of visual effects, 3D animation, etc. And yet they, too, aren't mining in their off-peak hours (and they certainly have the infrastructure to let mining only occur when no other computation is required, and the accounting people to throw it as a line item onto any contracts). They seem almost uniquely fit for the task. So why don't they?
That's where the second part comes in. Google, and Hollywood, make far more money doing what they do than they have factored they would stand to gain from mining.
I do think dedicated mining companies will pop up, especially once transaction fees become the primary reason to do so, rather than the mining effort - and Google may well become one of those companies. Until that time, though, they'd probably prefer to throw money at buying Bitcoin than mining it.
