StreetskaterFU has coded and released a very simple Linux USB logger which logs the USB traffic of every port. The USB logger does run on PS3 (in Linux). To sniff the GameOS USB you need a USB (Male-Male) cable, connected to PS3 to PC, and start the logger on PC (Linux only).
There are many things that can be logged and leads to who knows what, a few cases listed by SKFU below:
* PS3 USB at PS3 boot sequence
* PS3 USB to PC fake external HDD
* PSP USB at PSN Store downloads