What usages am I seeing in current edited prose: newspapers, magazines, websites, books? What do I see in the reliable authorities, such as the usage notes in the American Heritage Dictionary, Butterfield's Fowler's, the websites of editors and linguists recommended at this blog? What does Bryan Garner say? Though his personal preferences leak through a little in Garner's Modern American Usage, he is scrupulous about corpus research. If his Language-Change Index identifies as usage as Stage 4, "Ubiquitous, but …" you can be sure that you have arrived at a tipping point, the stage at which only the most conservative readers are likely to object.