Statistical/cryptographic systems, such as Language Weaver, calculate the probabilities of correspondence by examining parallel texts. They then "learn" these translation patterns and use them to translate similar constructs. But claims of extraordinary accuracy are generally not borne out in tests by professional, human translators.
The holy grail of MT is FAHQT: Fully Automatic, High-Quality Translation. For now, professional and amateur users content themselves with "gisting"—the practice of accepting 80 percent accuracy so as to get a general sense of a text's meaning. (Ninety percent accuracy leaves one error on every line.) Professionals who work with MT always do so in conjunction with human judgment, either by "pre-editing" to limit vocabulary or by "post-editing" to correct errors. In my job, where political sensitivity and nuance are everything, "gisting" would be worse than useless. On the other hand, I often use a dedicated memory-based system to translate treaty names, provisions of international law, and the like because they are directly correspondent and there's no risk of error.
There are plenty of computer scientists who think we don't need to settle for Not Really Automatic, Pretty-Mediocre Translation. Mike Collins of MIT, for one, has high hopes for "machine learning," which bypasses the need to hand-encode software by comparing broad databases of text previously translated by humans. In theory, this will allow the machine translator to learn grammatical rules. With vast oceans of multilingual text now available digitally—Collins cites documents created by the European Parliament—this may indeed be the best hope for MT, though it is probably still a long way from affordable commercial application.
Language Weaver CEO Bryce Benjamin acknowledges that even the best translation software cannot hope to replace human translators; it is simply one tool "to help them to increase productivity and value." That was all I needed to know. The war on terrorism notwithstanding, my job and those of thousands of professional translators in the arts, sciences, and industry seem relatively safe for now. But then again, horses were pretty damn sure of themselves 100 years ago, and look what happened to them.