When with other "real live" minders, my minding friends and I often have a general moan and groan about any minders who "misbehave" (probably because it makes us feel all holier than thou). Talking about perfect childminders just makes us feel inadequate, so we certainly wouldn't want to do that! Any conversation is very private amongst ourselves.
It's easy to forget that the chats on Mumsnet get read by lots of different people, not just other childminders.
The posts here can sometimes be fairly dire, but people will always post negative stuff or ask about problems. Not many parents are really going to start a new thread praising their childminder! (Can you imagine ... "my childminder wants to feed my child organic, free-range 10-vegetables/day meals, is this OK?)
I think I will have to do a namechange or two and come on praising myself.