Like the Atrix before it, Motorola’s new flagship device, the RAZR, has a locked bootloader, making it very difficult to get in there and mess with important system files.
As always, though, eager developers have solved, or at least side-stepped that problem, by offering a Bootstrap Recovery. What this means is that it is accessible through the main ROM and loads into memory only after booting up.
While the RAZR was not necessarily difficult to root, getting this custom recovery means that we are seeing an increased number of custom ROMs availame for the skinny device. Now these aren’t the same as on other devices as the ROMs must be based on the official software but they have a number of improvements over what the phone shipped with.
Source: XDA-Developers Portal