Here's an example, taken from some other forum I was reading: Someone had updated to the 2.01 version and noticed the laggyness of the browser, so they took the browser.apk from 2.0 and installed it in 2.01. Reboot- Brick. The official update .zip wouldn't update the file back to 2.01 either because of an md5 mismatch. This phone was bricked. If he had a custom recovery, he could have adb pushed the file onto the phone and would'nt even have to do a wipe. Woulda been a five min fix as opposed to a bricked droid. Oh, and that was very well put Boostdscoob.