Singular they has seen wide use for centuries starting with Chaucer and picking up Lewis Carroll, Walt Whitman, George Eliot, Shakespeare, William Thackeray, Jane Austen and Oscar Wilde along the way (list shamelessly stolen from http://motivatedgrammar.wordpress.com/2009/09/10/singular-th... ).

If you've only noticed it in the last few months then I suggest that you've not been looking hard enough!

The point of my comment was that I am certain that if you look hard enough you will find any number of nonstandard constructions that you would reject, despite it being included in Chaucer and Shakespeare.

I was already well aware of it's long historical usage, I simply would only rarely see someone say "Chaucer used it, therefore it's fine to use on a resume!" The spelling "aks" for "ask" is one such example that you could find nearly as many high profile historical usages, and no one argues that it is an acceptable spelling.

(Also half that list is exactly the kind of people that you would find an enormous amount of nonstandard usages; Chaucer is Middle English, Shakespeare was famous for writing in common vernacular, Lewis Carroll is famous for his literary nonsense and wordplay; hardly the best sources for what would be included in 'high' English)

Did you read the rest of the blogpost I referred to? Alternatively, Language Log has a whole category assigned to the use of singular they: http://languagelog.ldc.upenn.edu/nll/?cat=27

English is defined by usage; Singular they has very widespread use from the time of Chaucer to the present day. Only mad grammatical prescriptivists object to it :)