Someone mentioned this earlier and I'm finding it to be more and more true. With 8 playing, trading is a little tougher as we've eliminated 1/4 of the potential trade partner. Throw in the 6-8 who will only deal if they're destroying you in the trade plus the 4-5 who are either "all out rebuild" or "I'm gonna win now and leave" and we might less than half a world to trade with.