There is an old saying, a picture is worth a thousand words. This could not be more true than the image above.
If you are currently jailbroken or unlocked, do not update your firmware via iTunes to the latest iPhone firmware, 2.2.1. According to the Dev Team this update will indeed break yellsn0w rendering your unlocked iPhone useless.
So you have been warned, do not update to the latest Apple firmware if you are unlocked or jailbroken. Stay tuned to TiPb for more information, when it becomes available we will be sure to update you.