Answer:
They all have the problem that languages/words are ambiguous, and only context can (sometimes) avoid schoolboy-type howlers. The better ones (Google, Babelfish) manage to keep on the straight and narrow most of the time, but without human-to-human exchange, internet translation has the danger of bilingual thesauri 'talking' to each other.
For example, the word 'right' has multiple meanings in English - the opposite of left; OK; to correct (right a wrong); the opposite of wrong; the right to do/say things, etc., etc.
Although the internet grows a vocabulary via accumulation of examples, there is always the problem of the wrong meaning being attributed, and this becomes evident in the other language(s), where 'right' may not have exactly the same ambiguities.