So which mods which brick the iPhone/iTouch?

So between Steve Jobs threats to combat hackers and the "genius" (who had this annoying cocky swagger) at the local Apple store in Skokie gloating about how users that hack their iPhones won't get support and others will automatically be "bricked" when then run iTunes, it will be interesting to see what happens and how Open the platform? For me running arbitrary apps is the whole point of even buying one of these devices.