On ships I crew with random people all the time, but not really for the bonus - I've mastered sailing and need to up my cannon. Since I don't let strangers sail my ships, crewing for other captains is the way I've had to go. Unfortunately, even on a "good" crew everyone's using lighting and the enemy goes down so fast I'm lucky to get ten points. The alternative, which I've been doing more and more, is sailing alone, parking somewhere safe, and then sinking everything in the vicinity by myself. Better rep, but pretty darn boring...
I will crew with strangers in the cave, though, for points and easy ammo runs. I've actually made some good friends that way.
Also, LoL @ mongo's response. Too funny.