Yeah, Google basically bought *us*, as in our data. Years of it: Our biometrics, how active we are, how we sleep, how/where/when we use fitness devices, etc. This is all stuff Apple had to conduct its own surveys to figure out before Apple Watch, but now Google has it directly and can draw insights on how it can use that to target advertising and promotional information at us. Our concerns are minimal, it's only about holding enough of a carrot out to entice us to keep giving it to them. All our privacy and data usage agreements were with Fitbit, not Google.
A key component of Google's business is advertising, which makes me nervous about what that means for some pretty intimate data Fitbit has and is currently gathering on us. Not to glorify Apple, because it definitely has its issues, but Apple is much more reliant on consumer products and services, which is why they can be so strident and bold in their declarations on protecting privacy (I'll bet there are warts if you look more closely, though). I think this pretty much expedites my move off of Fitbit.
