Josh Bressers filled all but one block on his Sony flash drive, then kept writing to the drive until it failed and this is what he found out:

It took 90593104 writes for the drive to die. That’s 90.5 million, well beyond my expected 30K.

and:

I can still mount and read from the drive, but I can no longer write to it. It’s nice to know that when a drive dies, it’s more likely you just won’t be able to write new data to it, rather than complete data loss.

I wonder how consistent this is throughout all the different manufactures of these little drives.