Not accusing Google of doing anything untoward at all... it is a marketing business that excels at what it does -- to know everything pertinent and to monetize the power of knowledge.
But think if you were in the defense or robotics business -- to use as an example -- and an avid user of Google apps. Think you might reconsider building and parking your business plans and analyses with Google (to facilitate sharing among your team and all that) -- when you come across this? Oops - a new potential competitor who has all your stuff!
Some of us care more than others about our private data. There is no right answer. But for business use, I wouldn't put anything in a public cloud without first encrypting -- if I put anything in a public cloud at all.