Oh no... I am paranoid about my Galaxy S2.. :-\ 
We've contacted Samsung about the problem where performing a mmc erase could hardbrick your phone (i9100, i9100g, n7000, m250 - MAG4FA, VYL00M, and KYL00M with firmware revision 0x19 // T989 and I727 with fw rev 0x12) if it's having a faulty emmc chip.
Read this thread for more informations about it: http://forum.xda-developers.com/showthread.php?t=1644364

They're working as hard as possible on a clean solution which will be ready soon.

Please be patient and try to not flash any leaked kernels or kernels based on sources where MMC_CAP_ERASE is present.

This app http://forum.xda-developers.com/showpost.php?p=27014974&postcount=1 can be used to identify if your phone is affected or not.

CM9 kernels are safe to flash.

Please share!

Update 14:56 CEST:
Patches will be out in form of new official ROMs and also sourcecode releases after testing, which might take some time.
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