Much has been written, not least here, on the comic aspects of machine translation. And only yesterday I had a reference to the 'Slate Tower' (geddit?).
However far more insidious is the perfectly plausible translation that is simply wrong. I have two serious examples from recently.
'The value of the collection was assessed on the price it was likely to fetch if sold in Germany.'
Looks fine. Except that the German says: 'im Inland'. And we're in Austria.
'Half the money was to be raised by the government and the National Bank.'
That was also perfectly plausible in the context. Except, in the German was the little word 'je'. So the govt. and the bank were to find half the total each, not half the total together, which is the clear implication of the English sentence.
Machine translation can certainly save time, but it doesn't save intelligence or knowledge. You really have to look at every word. And the better the translation appears to be, the harder you have to look.