Uh, in both cases "not the user", your friend using any other system unless he decided to back it up would have been locked out anyway unless he was using a localised system like POP3... Most systems allow admins to block/prevent data exports one way or another. He could have copied and pasted the slack history if he wanted a copy as easily as he could have backed up gmail / irc / etc....

I think your argument is somewhat null....