No heads turn when someone says, “Everyone is bringing their own lunch.”
Except … it should be, grammatically speaking, “Everyone is bringing his own lunch.”
This brings up the whole question of our ubiquitous use of they and their as singular pronouns and possessives. As I noted, no heads turn when people use the plural to modify a singular antecedent.
I mention this after reading an interesting article in the New York Times, “Toppling the Grammar Patriarchy,” which describes French teachers’ rebellion over defaulting to masculine forms even when the subject includes both male and female.