Dictionary.com lists Gladwell in the etymology. However, Wikipedia's entry for "tipping point (sociology)" (which, to my knowledge, is effectively the same as

Dictionary.com lists Gladwell in the etymology. However, Wikipedia's entry for "tipping point (sociology)" (which, to my knowledge, is effectively the same as Gladwell's use) says, "The phrase was coined in its sociological use by Morton Grodzins, by analogy with ..." The page on Grodzins says, "He is known for coining the term "tipping point" in studies of white flight, such as The Metropolitan Area as a Racial Problem (1958)". No doubt Gladwell popularized the phrase, but I don't think he coined it by any means.