One further thought; when I see "..well they call in and ask 'can you do this, can you do this, can you do this?" and "certain people try to manipulate the rules"-- what that says to me is they are trying to get the agent to bend (or break) the rules and/or trip the agent up (overnight stopovers, transit vs. stopover, etc.) That exact person is the same person who would have a high likelihood of trying to play around with the ticket once they have it, and, in some cases, get caught doing so-- and maybe even doing so on a repeat basis..
But as far as a prophylactic banning of some folks based on them working the system "legally", I don't buy it. But I'll ask and find out.