Excellent news, folks. The bootloader on the Samsung Nexus S (watch our hands-on video) can be unlocked just as the Nexus One's was. Gandalf44 in the Android Central Forums reminds us of the instructions:
1. Shutdown the phone
2. Hold down volume up + power
3. Now you are in the standard recovery mode
4. Assuming you have 2.3 SDK installed with fastboot (Google around for that info..), now on terminal/windows or Windows cmd depending on OS type "fastboot devices" to check your device can be seem via USB
5. Assuming you device is seen via fastboot devices, now type "fastboot oem unlock"
6. Accept ... and new bootloader is unlocked...