Ultimately, you've ALWAYS got to trust someone. I mean, let's be honest here. The iPhones are assembled in factories in China, using many foreign components. Are you 100% positive all of those chips in your iPhone are not counterfeit or rigged with some sort of "back door" the right person could exploit?
There's a big issue right now with the U.S. government, where they installed quite a few Cisco routers that turned out to have counterfeit parts in them. If they can't even get a known secure product, how do you know your non-jailbroken, consumer-grade iPhone is?
At the end of the day, I look at the risk / benefit ratio of taking different avenues, and the jailbreakers offer me with what seems to be a far better deal. Can I trust the "nameless" people who write that code? Obviously not 100%, but I *do* have the power of the "community" backing me up. (EG. If someone figures out they're being less than honest with one of their programs, there's a good chance word will leak out on one of the many forums set up to discuss those topics.) On top of that, I see a lot of evidence that the folks developing apps for jailbroken iPhones are acting on principles of their own. They want an avenue to sell their code on their OWN terms, instead of only after agreeing to Apple's terms.
