Yet another entry into this cultural skirmish: The Vocabula Review — September 2003 — Singular They: The Pronoun That Came in from the Cold — jjoan ttaber altieri
“[N]ative speakers of English automatically rely on singular they (their, them) as the pronoun of choice.”
I prefer the commentary by another Quaker member of copyediting‑l, that people don’t seem to have any problem with singlular “you.”