A company can damage an open source project in a number of creative ways that have nothing to do with file formats. One word: Oracle. OpenOffice vs LibreOffice is a pretty good example of plausibly deniable sabotage that would enjoy a bonus with the number of people interjecting, index finger raised, with "Actually, Hanlon's razor..." To be fair to Oracle, Sun didn't help that situation at all, Oracle just ratcheted it up.