i think you all miss the point this worm was a clever attempt to educate people not to install ssh if they arent going to change the password.
It's really your own fault if you get infected, it's just like running a PC and visiting whichever site you want, and downloading whatever you want to without a firewall.
Seriously, everybody that wants to jailbreak their iPhone should be tested for clevernerss, why not just advertise the details to your bank account whilst you're at it?
Leaving a device that is almost constantly connected to the internet open to anybody and everybody that wants to hack it by not changing a password, what is the world coming to?
Will Apples iPhone be exposed to more virus attacks in future? I would definitely say YES. Will iPhones without a jailbreak be the primary target? I would say NO (or at least not yet). The "proof of concept" we see right now is just the beginning (my personal opinion). I believe that we will see a lot more attacks in the next weeks/month cause there are a lot of dump people out there using a "cracked" device without knowing anything about what they have done to make it work. It's nothing bad to have a jailbroken iPhone but you should have at least a basic understanding of what you are doing and you should definitely read the manuals.
The awareness which is created right know is not bad but you also have to see that the same people now will try to secure their devices with passwords and i think most of them will have 1. a hard time doing this (don't belive that someone who gave is phone to a "geek" to get it unlocked for money will be able to change his password on his own) and 2. will not use a complex password at all leaving the device open for attacks again. Even people you performed the jailbreak themselves often do not know what they are doing - if you want a proof just check the iPhone Dev teams website and read the comments ;-)
Why will Apple not be in the line of fire on this first wave?
Cause they are keeping their devices locked. It will be much harder for someone to break into those systems cause the ways on how to get in will lead you through the AppStore or you have to have really good idea on how to break in otherwise (Mail, MP3 or Photos/Videos might also work but this is far beyond the capabilities of the usual scriptkiddie...going through iTunes also might be a way but again you need to be skilled to do so).
This strength is also Apples weakness ;-) They force the people to crack their devices and people don't crack their device cause they want more functionality or use illigally gained applications - they just want to use their phone with the provider of their choice (yeah you can buy iPhones without a contract for prices you can also buy used cars and some providers also offer you an unlock but look for example at AT&T - they will never unlock your phone even if your contract runs out).
As long as this is the case we will see jailbroken iPhones being in the center of attacks - and we might also see more malicious stuff going in. But these kind of problems have nothing to do with Apple.
As soon as the non jailbroken devices will be exploited this easy then it's Apples problem but i think then many of us got much bigger problems ;-)
Just a little addition for fun - why should someone write some kind of virus/trojan for the iPhone? As far as Apple said the got their own backdoor into every Phone ;-) and if you want to gather non personalized information about the iPhone usage just write an App which gathers as much information as allowed by apple (at least one part of this "non personalized" information is your phone ID which is quite unique :-p)