As far as I\'m aware, flashing only works from CF cards so you will need to get a CF card anyway. This is not bad, however.
It is good practice to have one card for flashing and a separate one for general storage needs. Why? Flashing can only be done with cards that are formatted using the FAT filesystem which, among other drawbacks, doesn\'t support symbolic links. Software installed onto a FAT-formatted card may not work. So you either need to have a card with 2 partitions (one FAT and one, say, ext3) or you need two separate cards.
Given that you only need 16MB to flash (well, apparently you need more for certain ROMs), you should hunt for any old 16 or 32 MB CF card at the lowest possible price. Then get yourself a good, reliable SD card for other stuff.