With this exploit, although its run in a "sandbox", can it access files? If so, can it write to files? If it could, it would make getting into areas previously only accessable with the geohot exploit possible to the average end user.
If the images it needs can only reside in the "loadme.fu" file itself, would it be possible to domehow corrupt the USB to make it read further than whats actually there, say getting a 512mb USB, and putting a "loadme.fu" file that is supposedly 4GB on it (mess with the partition file headers, it's definitly possible, my USB has become corrupted before and had massive files appear that cant be deleted)?
From there, if the PS3 loaded something dodgy, like RAM or part fo the harddrive when it exceeded the size of the USB, you could get the loadme.fu file to read from that area, and show it on the screen, maybe even write to it. It's all hypothetical, and I don't really know the PS3's security, but it may be worth a try. Just my noob thoughts on the matter.