Listen, whether this is a ponzi or a huge mining setup, it's not worth it.  It's a fun system for people just starting to get into BTC to say they can be apart of cloud mining.  I look at it as a step up from faucets.

Facts
On 2/24 I bought 0.26 BTC worth of mining services from PBmining, on 3/3 I bought another 0.24 worth of mining....quick math:  0.50 BTC.
I currently have been paid out  0.22089736 & 0.21881598 respectively.....totaling:  0.43971334.
My last few payments have been: BTC0.247 (5/4/14), .0237 (5/11), .0214 (5/18), .0198 (5/25), .0174 (6/1), .0170 (6/8).


Am I tracking to make money/btc in the long run?  Most likely.  But how much?  Fractions of a BTC, maybe.  I might even just break even.  Giving PBmining the benefit of the doubt bc they have been a friendly service, lets say my contract stays in service for 5 years and I make 0.1-0.2 BTC, is it really worth it to wait 5 years for that little of BTC?  Not IMO.  

To each his/her own, those are stats from my account after 3+ months and my opinions too, enjoy.