Those things can be manipulated. Take Genesis as an example - https://bitcointalk.org/index.php?topic=768281.140
Their CEO invited Gavin Anderson to their mining operation, to validate what they doing. Total transparency from this company, gives physical proof, that they mining, what they posting on websites.
If you have proof, that PBmining are doing the same, feel free to post it here, and I will strike through everything I posted on here about them.
To me, PBmining is a Ponzi and no different than Tradefocus or any other HYIP / Ponzi doing the rounds.
We just choose to look the other way, when a company exist for a long time.
I have been long con'ed with Ponzi's before, and they lasted more than 2 to 3 years and yes, I still play with it, because I know the risk involved.
Is this ethical? Most certainly not, but it's in no more ethical than using PBmining and saying that it good.
It's a low yield high risk investment program then?