No doubt it's a hard time to mine...I'm no where near profitable right now, just trying to get through the hard times.  As far as rentals, we've had this conversation.  Don't think that's a factor.  Alot of miners we lost are in the range between U and me (35-50th)  and the big boys  (say .5Ph).  I'm concerned that those are an important part of the user base.  I wish I could look at some other pools hashrate distribution stats for comparison (ie slush),  If this is an industry wide issue, then oh well.