Unlocked iPhones (temporarily?) iBricked.

"As Apple warned earlier this week, the latest firmware update did, in fact, 'break' unlocked iPhones and kill unofficial 3rd party iPhone apps... The folks who unlocked their iPhones and who were installing 3rd party apps were the early adopters who were most likely to go out and evangelize the device -- especially if it was more useful thanks to alternative networks and better applications."