I had this thought while reading the CO visit thread, and decided to make it a separate topic.
How much longer can they keep beating the slaves before there is a rebellion? It is obvious that the trickle of people that are leaving is growing, and growing enough to make them worried. At some point it may become a flood. When people start reallizing they have more friends outside the Borg than in it they may vote with their feet.
Another big problem is the fact that seem to be loosing their children. This has killed off more than one movement in the past. When the last tired old member is dead, there isn't anything left.