Why can't this be done via USB?
...or more precisely, why hasn't it (assuming it hasn't..and I'm not behind the curve on this sort of thing) yet been attempted?
What you ask?
A USB file transfer browser. A homebrew app that allows you to copy files to the PSP's folders via a generic USB drive...be it a USB thumb drive or a full-on portable 80 gig hard drive.
I know there are portable hard drive's with built-in transfer abilities..but those are a lot more expensive. What would be better for a long trip than to take along a spare hard drive filled with PSP movies and other apps, and simply download different games movies to your memory stick as many times as you want?