I trust Google to honor their terms of service which is all we can really ask for I think. Outside of that, I trust them as much as any other large company with a profit motive. Which is to say about as much as I trust my dog watching the Thanksgiving turkey while it cools.
I trust Google to honor their terms of service (which are not the same as what I first agreed to) for as long as it doesn't benefit them more to break them and take the consequences.