Hummmmm....I haven't read anything on the partioning of the drive, but drawing on my knowlage of computer hardware, I think that the limitation is not in the firmware of the psp, but in the partion itself. By default, the psp formats it's drives in the FAT16 partioning style. Because FAT16 is so old, it has a limit in the space of the drive which it's on (in this case, 4 gigs). If the psp will recognize FAT32, then there is a maximum drive space of 2 Terabytes! If someone would like to test converting a FAT16 to FAT32 memorystick and seeing if the psp recognizies it, please post it. Personaly, I see no way for this to brick your psp. But don't hold me to it.
If you want more information on FAT, go here : http://en.wikipedia.org/wiki/File_Allocation_Table

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