For forensic use I assume the cards have serial numbers, otherwise you could simply copy the data off onto a PC, tamper with it, then write it back to another card and conveniently lose the original.
Of course to simply avoid erasing an important recording on a normal SD(HC) hard, click the write protect tab across. I wonder how easy it is to break them off to prevent accidental switching back? After 5 years copy it to another card to refresh the data. After another 5 years copy it to the credit card size terabyte archival storage medium they will have invented by then.