You can't blame Apple too much for its stance on the recently released virus that attacks iPhones. Apple noted that, "These hacks [jailbreaking] not only violate the warranty, they will also cause the iPhone to become unstable and not work reliably." If you don't jailbreak your iPhone, this virus isn't going to be a problem for you. That means most people (92% - 94%) should be safe.
Because jailbreaking installs SSH networking software, there is a password vulnerability that is easy for viruses to circumvent. There is an easy step to take, however, to a protect jailbroken iPhones. Users can go to Cydia to download and the install the MobileTerminal app. Once that application is installed, users only need to the default password from "alpine" to pretty much anything else.
If you're taking the risk of jailbreaking your iPhone, it isn't that much more work to provide yourself with at least a modicum of safety.