Where there is a will there is a way with the bootloaders.
to an extent. ways have been found to gain access to /system/ and even change kernels, but you still have no access to other partitions. recovery in locked bootloader devices is not a real partition that will always be there as it is when you have fill access to things. thats why when things go bad on a locked moto or sami you just have to flash yourself back to stock and start over.
feel free to post up other questions you may have after reading thru the tereminology post in the how to thread linked above. but in a nutshell:
locked bootloader means only flashing things that are signed and approved by that devices mfgr. in other words,you can flash a radio or recovery,and in some case youre even limited on wich stock RUUs you can run.
however,having a locked bootloader does not prevent you from making changes to /system/ if exploits can be found to gain access to it on whtever firmware the device is running. with s-on,you can still flash roms,and even kernels in most cases and run root only apps.
unlocked bootloader is pretty much wide open. you can flash whaever software you wish,older or newer RUUs,you can flash single partitions that wernt approved and signed my the mfgr. i.e.,you can flash a new recovery,radio,or bootloader via an unlocked bootloader.
rooting devices with a true unlocked bootloader is rediculously easy. you just flash your self a new recovery,then use that recovery to place the needed root files into/system to continue on a stock roted rom. or you can simply flash custom fimrware from the beginning,immediately after flashing the recovery. there are no exploits,hacks,or downgrades needed.
samsung has made efforts to keep its bootloaders open for the community. htc,while locked down in most cases,have been proven fairly hacker friendly,with workarounds and methods in place for most all devices to unlock the bootloader. motorola has gone a step further and encrytped its locked bootloaders,making it nearly impossible to crack. to this day,the droid 2,x,etc. despite all the advnces and even full CM support are still equipped with locked down bootloaders.
hope that helps clear it up a lil. i personally will never buy a device whos bootloader i cant unlock.
