We searched 'in vain' for the missing earring. [=we searched for the missing earring but did not find it]
Her suffering will not be 'in vain'. [=something good will happen because of her suffering]
('humorous') I thought I heard someone 'taking my name in vain'. [=saying my name]
(..) on some save-the-world vanity project? He can't get your money back. I can. I could try explaining that a save-the-world project, vain or not, is worth investing in, Mr. Daggett. But you understand only money and the power you think it buys, so, why waste my time... indeed? Second shift reports in? (..)2012 The Dark Knight Rises