What are the consequences of installing CWM?
fastboot oem unlock always deletes userdata for security reasons, so it must be used only once (until you lock again manually).
CWM is needed if you want to flash a root package (you can't push it via fastboot), but that is not usually the only way to root a device.  The CWM install needs only the fastboot flash recovery recovery_name command, which does not affect user data.