Actually, not really. From what I know, the keychain security hasn't been broken, except through brute forcing the passcode. While that's usually possible for the standard 4-digit passcode, it's not always possible. Jailbreaking is a necessary step to get the access necessary to brute force, but it doesn't magically break open the device for full access. (However, I am not an expert at this. I've talked with NerveGas (http://www.iosresearch.org/), but he's the person who really knows the most about that kind of stuff.)
A lot of what people are trying to protect is stores in the clear, though: I personally don't want people piking up my phone and stealing my address book and photos. Google's approach to this, a supported "jailbreak" (fastboot oem unlock) that formats the phone as it does its job, is tome the best solution, as it guts the incentives of people like comex to weaponize an exploit so well that any evil idiot can use it (in essence, the only people with the technology would be the "larger evil", as opposed to people like your nephew, ex-husband, or business rival).
