Glyn Moody writes: If open source is such a success, why aren't there any billion-dollar turnover open source companies? A recent briefing by Red Hat's CEO, Jim Whitehurst, to a group of journalists maybe provides an answer. Asked why Red Hat wasn't yet a $5 billion company, as he suggested it would be one day, he said getting Red Hat to $5 billion meant “replacing $50 billion of revenue” currently enjoyed by traditional computer companies. If, as is likely, that's generally true for open source companies, it means they will need to displace around $10 billion of proprietary business in order to achieve a billion-dollar turnover. Few are likely to do that. Perhaps it's time for managers of open source startups to stop chasing the billion-dollar dream. If they don't, they will set unrealistic ambitions for themselves, disappoint their investors and allow opponents of free software to paint one of its defining successes – saving money — as a failure.