Interesting explanation
here as to why Google Translate tends to produce better transatlions than its competitors.
To save you the click, here's the (simplified) summary: rather than itself translating your element of text, instead it finds a place where your element occurs in its massive corpus of scanned literature and online documents, then looks for an existing translation of that document, and gives you back the corresponding section. So in effect it is drawing on the work of past book and document translators, and on the unoriginality of language use.
(Of course, a lot of the time it won't work, where there's no match or no translation into the requested language. But I guess they've worked out that it succeeds often enough to be worthwhile.)
Poll Traduttore and/or tradittore? (Thanks to
crowleycrow for spot.)