Well, the BSD license model explicitly allows others to take your code and bundle it and release it however they see fit. There's nothing to stop someone from taking Postgres, for instance, and bundling it up into a licensed, close-source product.
The GPL prevents that, but there has never been a definitive court test. You keep hearing rumors of companies attempting to do this. The FSF solicits such reports and follows up with the supposed perpetrator. So far nothing's gone to court, presumably the stories are largely red-herrings or the company involved responds reasonably once the situation is explained to them (you'd be amazed how many license violations, in all worlds, not just the open source world, result from ignorance rather than intent).
All software will be stolen, you can depend on it. There's no reason why this shouldn't happen with GPL'd software just as it does with software distributed under closed licenses. Photos are stolen, books are stolen, music is stolen ... on and on and on.
