Many of us who own the Galaxy Nexus probably have the Bootloader unlocked and have it rooted as well. I know mine is unlocked, rooted and running CyanogenMod 10. But some people who have had older devices may not want to unlock the Bootloader because back in the day Bootloaders could not be locked and unlocked at will. So if you want to root your phone and not lose all your data this is also a good alternative for you.
Now the Galaxy Nexus' Bootloader can be unlocked and locked at will. One of the biggest advantages to rooting without unlocking the Bootloader, is that you won't have to lose your data. Thanks to XDA Forum Moderator efrant, there is now a new method to root your Galaxy Nexus without unlocking your Bootloader. The process is a bit longer than usual.
In short, you're going to push some files on to your device. From there, you're going to restore a fake backup, run an exploit that'll reboot you into emulator mode where you'll perform the rest of the steps.
So those of you who own the Galaxy Nexus and haven't rooted it yet, go ahead and try this out. You can find all the information in the original thread over on XDA's forums.