This is a topic that the masses will never agree on, that's ok. IMO if you are "trying" to keep smaller plants and growig sog, you should definately trim the fan leaves. If you are growing larger plants, and you want multiple colas, well I still dont thinking pruning most of the fan leaves is a bad thing lol, check this thread out. It is a grow journal on another site, and the grower trims half of his crop and does not trim the other half, he basically tests the arguement for us. Well as you can see, actually ya I'll let you read it. Start from page one it's a solid journal, but on the page that I posted here he supplies pictures for you and even states himself that the plants that had their fan leaves removed are clearly not showing any signs of less bud production. At the end he compares the final harvests and you can see the results for yourself...
http://www.420magazine.com/forums/completed-journals/138874-come-sog-me-112-plant-2-liter-hempy-sog-11.html
*I understand that this does not prove anything. I mean this is one test on one strain in one environment by one man, or woman. Who knows maybe this strain they used grows bigger without fan leaves and others do not, or maybe rmoving fan leaves does not reduce the overall size and or quality of the plant, tough question.