How can I unbrick my Droid Bionic?
I fixed it.  Here's how:


Download moto-fastboot
Download the images for stock Motorola Bionic into the same folder you downloaded moto-fastboot to
Open a Command Prompt to that folder and run the following commands:



moto-fastboot flash mbm allow-mbmloader-flashing-mbm.bin
moto-fastboot reboot-bootloader
moto-fastboot flash mbmloader mbmloader.bin
moto-fastboot flash mbm mbm.bin
moto-fastboot reboot-bootloader
moto-fastboot flash cdt.bin cdt.bin
moto-fastboot erase cache
moto-fastboot erase userdata
moto-fastboot flash lbl lbl
moto-fastboot flash ebr ebr
moto-fastboot flash mbr mbr
moto-fastboot flash devtree device_tree.bin
moto-fastboot flash system system.img
moto-fastboot flash boot boot.img
moto-fastboot flash recovery recovery.img
moto-fastboot flash cdrom cdrom
moto-fastboot flash preinstall preinstall.img
moto-fastboot flash radio radio.img
moto-fastboot reboot


My problem was that I downloaded the wrong stock images for my Bionic.  I initially downloaded VRZ_XT875_6.7.246.XT875.Verizon.en.US_CFC_01.xml.zip but those image files gave me "preflash validation failure" messages.  6.7.246.XT875 was the previous stock version my phone was on.  But prior to rooting, I had upgraded to 98.72.22.XT875, which was not backward-compatible with the previous version.  As such, once you upgrade to the latest version, you can never go back to the previous stock version.

The stock images I should have downloaded were cdma_targa_9.8.2O-72_VZW-22_1ff.xml.zip  Once I downloaded these images, I was able to run the moto-fastboot commands successfully.  

My phone is now running the latest stock version.  I don't have root anymore, but that can change :)