I thought a little perspective from a noob might be useful. I learned about CC a couple of weeks ago from some friends with free time at work, and played my first couple of games only with them. Got lucky with an early win and made PFC before I knew what it was. Since then I've stretched my wings a little and sunk to Cadet.
There aren't any guidelines about what kinds of games to join / avoid. As a common-sense measure, I stuck to options similar to a board game (ahem...) I've played from time to time. I stayed on boards with simple bonus and movement rules (e.g. Great Lakes). I didn't know it was possible for anyone to invite me to join games; wasn't aware of the Callouts forum (still haven't been there...). I don't *think* I've been farmed - I've just been more enthusiastic than skilled. Anyway, it might be good to have some guidelines in the Instructions section somewhere. I suspect it might do more good to (subtly) show noobs how to avoid farmers than to try to enforce subjective rules against the practice.
A clearly marked area restricted to, say, people who don't have any achievement awards, would have helped to make me feel capable, whether I won or not. After three or four losses in a row, I was feeling like dropping off and not playing any more. Then there were a couple where I wasn't totally outclassed from the beginning, and so I'm still here and I think I may have a chance in one or two of the games I'm in now.
I guess what I'm rambling on about is that as I read through this thread, it seemed to me that the intent of the new rule was less about farming and more about retaining people after they show up, and lose a game or three, and realize they could participate a *lot* without ever gaining any wins, points or clues.
One last point from a noob's perspective -- it takes a lot less courage to join someone else's game than it does to pick a board yourself, figure out what options might be fun, and then wait a couple of days while everyone ignores you. Guys, don't stop putting up new games for new people just because you might get accused of farming.