I have met some good people by joining random crews or letting randoms join mine but I have also met some real numpties too.
Last night, me and two pals were doing Order of Souls voyages and decided to start a four man galleon in the hope of getting a decent random. At first we got a 'funny' kid who had a serious case of ADHD and kept talking incessantly. It was kind of amusing and after a while it was like white noise that you just tune out of. He left and nobody else joined, but then later on as we were mid way through killing four captains one of our crew got DCed and two randoms joined. One of them immediately said he wanted to boost and demanded we go to an outpost instead of helping us finish the mission. He even tried to set off with our galleon. We couldn't brig him as the other person didn't seem to understand or care what was happening. So we had to wait, me hanging on to the helm and my friend keeping the anchor down so he couldn't drive off. After 10 minutes the other random left which meant we could brig the offending numpty. The slightly annoying thing was that he then refused to leave, meaning we had to allow him a share of the loot. We weren't in a big hurry to cash in, so we made him wait as long as we could before we did.
I can understand that a kick option could be abused and that Rare doesn't want to add it, but the ability to lock and unlock crew slots would at least be a viable option, so that when a team mate gets DCed we can at least lock it down to invite only until they get back in.