> I "lost" several NAND chips during my development. I simply hacked the 
> FLASH erase utilities to ignore the ignore markers and erase the bad 
> blocks anyway until I got everything working and "rescued" the chips.

I've done bringup/development work on several boards using different 
arrangements of NAND.  IMHO, you will "destroy" at least a few chips in 
early development by having to erase falsely marked bad blocks, and at 
the same time erasing manufacturer marked blocks.  I've not noticed any 
significant errors by erasing manufacturer bad blocks, and you shouldn't 
be too worried about it.  That said - I also wouldn't let any of those 
"destroyed" chips out into the world in a real product.

Cheers
Brad