I'm very careful about who I friend (Sorry, I won't accept random friend requests.), so I don't mind it when someone teleports to my ship without asking me. (The extra money I get from having a crew is always welcome.
)
I am always happy to have someone helping me to take down a ship. Every bit they help means less HP loss for me, and that translates into less expense when it comes to fixing the ship.
I think the rush to get the rights to board a flagship, makes the game more fun! I'm never upset if someone else gets the ship, I'll just go find another one. There's plenty more in the ocean.
The newbie pirates crack me up though. When I launch my big ship there's usually a few light sloops with new players (I assume they're new, with low levels.) in them firing at me. "I'm not a Skeleton ship!". :P