its not about what google will do, you know secure institutions get infiltrated all the time, google knows all so if you want to get dirt on someone you go to google. Plus remember google the companies ideals aren't the same as Jeffrey on the 3rd floors ideals who got shafted out of a promotion and was demoted to night shift.
It's not that google are bad, they may or may not be (you do realise people and companies that are bad don't just come out and say, hello there I am bad, right?) its about the consequence or danger of having all that information in one place.
OK so you being some common web developer working for some crappy small company in South Africa have not too much to worry about, but google communicated with goverments, it has to. So if you're Joe Average in China and search for "human rights" or "civil action" and the like (which are all filtered by google in china) the goverment knows who you are, it can use that information to target you as a person capable of treason or something.
Also remember one thing, your data starts out and lives at google but once its 3 months old (anything, from your gmail to web habbits) can be accessed by the US goverment, so sure you trust google with all that data because they "don't do evil"... but do you trust any goverment with it?
Don't get distracted by shiny toys while some company collects all your data (imagien all the conclusions you can draw on someone from web habbits and emails etc) I don't care if its mother flipping teresa who has the data, if its all in one place, its a bad thing.
Power corrupts, absolute power corrupts absolutley