25. A computer system comprising: a non-transitory computer readable storage medium on which is provided a language model database to store a plurality of language models corresponding to a plurality of languages, each language model including information usable to determine a score reflecting a probability that a document is in the language corresponding to that language model, the language model database being further to store an impostor profile associated with each of the plurality of languages, wherein the impostor profile for each of the plurality of languages includes a parameter set comprising values characterizing a score distribution expected for documents in that language when scored using the respective language models of one or more impostor languages in an impostor set associated with that language; and control logic coupled to the language model database to compute, for at least some of the plurality of languages, a document score for a test document, the document score being computed based on at least some of the language models stored in the language model data store, and to select a most likely language for the test document based on the computed document scores, wherein document scores are also computed for the impostor languages in the impostor set associated with the most likely language, the control logic being further to compare the document scores computed for the impostor languages in the impostor set associated with the most likely language to the impostor profile for the most likely language and to determine whether the test document is in the most likely language or in no language based at least in part on a result of comparing the document scores.
25. A computer system comprising: a non-transitory computer readable storage medium on which is provided a language model database to store a plurality of language models corresponding to a plurality of languages, each language model including information usable to determine a score reflecting a probability that a document is in the language corresponding to that language model, the language model database being further to store an impostor profile associated with each of the plurality of languages, wherein the impostor profile for each of the plurality of languages includes a parameter set comprising values characterizing a score distribution expected for documents in that language when scored using the respective language models of one or more impostor languages in an impostor set associated with that language; and control logic coupled to the language model database to compute, for at least some of the plurality of languages, a document score for a test document, the document score being computed based on at least some of the language models stored in the language model data store, and to select a most likely language for the test document based on the computed document scores, wherein document scores are also computed for the impostor languages in the impostor set associated with the most likely language, the control logic being further to compare the document scores computed for the impostor languages in the impostor set associated with the most likely language to the impostor profile for the most likely language and to determine whether the test document is in the most likely language or in no language based at least in part on a result of comparing the document scores. 30. The computer system of claim 25 wherein the control logic is further configured such that determining whether the test document is in the most likely language or in no language includes applying a chi square test to the computed document score for the most likely language and the respective computed document scores for the languages in the impostor set associated with the most likely language L0.