Wow, lots to cover. I believe Mary is correct. If someone fouls you and you don't call him because he's your buddy, you both can be protested by someone else. This protects the fleet.
I personally think B Fleets are very important. In our area it's very difficult in A Fleet and most of the top sailors have 20 years racing experience. Having a newbie come into the jungle just scares them away. We have fleet races every week where everyone sails together and then discuss what happened over beer at the end of the day. When the B fleet sailors go to a regatta they have a chance at a trophy. I think this is very important to motivate them to stick around. I have never met anyone that was happy with last place. There are guys happy to stay in B fleet, but not always be last.