the reason they cant block SM is because its coded as "Crazy taxi for ps2" if they did block SM it would also block that game......
as for not being usb 2.0, ps2 only has/uses USB 1.0, in order for it to use 2.0 there would have to be some more EXTREME mod/hacking done, to make the ps2 side use 2.0 ports .
when a ps2 game is inserted into the ps3 & boots, the ps3 is basically a ps2, except for the PS menu, thats also the reason you cant get to in-game XMB while running a ps2 game
i still say that if you install/play a game that is a Ps2 title that is able to utilize the ps3 HD (one of the Final Fantasy's) it basically takes a chunk of the ps3 drive & formats it into the ps2 format. There fore if you load Ulaunch or somthing similar, Ulaunch should be able to browse that "ps2" partiotion on the PS3 drive.....i dont not have a game that can utilize the ps3 HD, so i have not tried this yet, but in therory it should work