...until someone finds a way to exploit it, as has happened with CD's "weak sector" copy protection schemes. It's only a matter of when it will happen, not if.
Corrupting the storage of a test pattern isn't particularly useful. MAYBE, you could cause premature tagging of bad blocks wearing out a flash drive/card faster. If the system you are using is allowing these kinds of writes to your storage device you have more pressing issues.
Only the most primitive SD/flash drive controllers actually use this scheme anyway -- encryption is much better at randomizing.
...until someone finds a way to exploit it, as has happened with CD's "weak sector" copy protection schemes. It's only a matter of when it will happen, not if.