I live with one for whom language is so fascinating that the recent release of the 15th edition of the Chicago Manual of Style and the 11th edition of Merriam-Webster’s Collegiate Dictionary have become major household events. The latter has been (harshly) reviewed in the Weekly Standard by the editor of the on-line Vocabula Review. The whole piece is worth reading, but especially nice is this contrast between language liberals and language conservatives:
As most people know by now, dictionary makers today merely record how the language is used, not how the language ought to be used. That is, lexicographers are descriptivists, language liberals. People using "disinterested" when they mean "uninterested" does not displease a descriptivist.
A prescriptivist, by contrast, is a language conservative, a person interested in maintaining standards and correctness in language use. To prescriptivists, "disinterested" in the sense of "uninterested" is the result of uneducated people not knowing the distinction between the two words. And if there are enough uneducated people saying "disinterested" (and I’m afraid there are) when they mean "uninterested" or "indifferent," lexicographers enter the definition into their dictionaries. Indeed, the distinction between these words has all but vanished owing largely to irresponsible writers and boneless lexicographers.