So Motorola spoke up on the Droid X's eFuse issue: if you install unapproved ROMs on your Droid X, your phone won't break. It'll just go into recovery mode and be unusable until you install Motorola approved software. Gee, thanks Moto.
The official word:
"Motorola's primary focus is the security of our end users and protection of their data, while also meeting carrier, partner and legal requirements. The Droid X and a majority of Android consumer devices on the market today have a secured bootloader. In reference specifically to eFuse, the technology is not loaded with the purpose of preventing a consumer device from functioning, but rather ensuring for the user that the device only runs on updated and tested versions of software. If a device attempts to boot with unapproved software, it will go into recovery mode, and can re-boot once approved software is re-installed. Checking for a valid software configuration is a common practice within the industry to protect the user against potential malicious software threats. Motorola has been a long time advocate of open platforms and provides a number of resources to developers to foster the ecosystem including tools and access to devices via MOTODEV at http://developer.motorola.com."