I absolutely hate when this plural word is used to mean something singular, and I refuse to use it that way.
Yesterday Anderson Cooper was widely quoted as saying this: "I've always believed that who a reporter [singular] votes for, what religion they are, [plural] who they [plural] love, should not be something they [plural] have to discuss publicly. As long as a journalist shows fairness and honesty in his [singular] or her [singular] work, their [plural] private life shouldn't matter."
OTOH, I think he's a fine reporter and a brave man. His grammar bothers me much more than who he loves, votes for or prays to.
Update (7/5/12), from a publishing company: "What are the challenges for a self-published author marketing themselves?"