Bottom line is - Rely on them? Yes; Trust them? No.
I trust they are not abusing the data they record about me, but I do not trust in the good of harvesting and data mining said data.
A clearer question would be "what do you expect Google to do, how effectively and consistently do you expect them to do it, how well does that serve you and what alternatives do you imagine?"
As for the Analytics/Docs etc. I use them because my clients do and I don't have many other places to point them to.
As for Trusting, what I mean is that I think that they would breach my privacy if they wanted/had to. It's a corporation that profits based on its user data, so I wouldn't be they'll look after their users if it affects their bottomline.