To most trading is just a boring grind. They want to get credits as fast as they can so they can do whatever is fun for them. Is there anything wrong with that? Absolutely not. We all play this game to have fun after all.
And about the PvP aspects of trading factions. Sure they could join your faction and pew on pirates, but you are still very limited. For example, I'm sure you wouldn't see a USI escort defending Texas or staging a raid into Rheinland.
About all you can do is try to make it fun for the members you do have. Perhaps you can set up special contracts or events.
Oh, one more thing. I'm not sure if USI does this or not, but set up a recruitment ship in Pennsy. The past two times I logged OSI's I landed two great new members.
EDIT: I know that was more info than what you were looking for. I blame me being dead tired. Sorry
![[Image: osi-hiring.png]](http://i705.photobucket.com/albums/ww54/Stygian0/osi-hiring.png)