Google translator is as bad as the translated snippets you give it. It's great for short sentences but anything further than that is a coin toss.
To explain what's wrong with it, basically, GT looks online for people who have already translated that given document or for pages that have similar metadata and applies a very small state machine translation, whereas other websites like babelfish used to have extensive and very complex algorithms that would try and replicate human speech.
Problem is, the former solution is much faster than the latter, and the big G knows that its users want to waste as little time as possible, at the expense of precision. Machine learning may at some point give us good translators that don't take forever, but it's pretty hard.