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.