It's assumed a Ponzi because of the fact we don't see TXN ID's, a lot of their "behind the scenes" operations are very questionable. Not to mention that by having others say "I'm getting paid, why do you think it's a Ponzi?" it builds their reputation to attract other customers. The earlier customers get their ROI, but newer customers may not. Because the BTC paid by newer customers feed to the older customers, not to mention they might have a storage of BTC that maybe they stole or something, and are finding a way to "give it out for free" sort of thing. What happens if they stop getting income? Their prices and contract lengths are too good to be true for a legitimate mining operation, unless they're getting free or super incredibly cheap electricity.

I've e-mailed them myself about this, and wanted clarification. I suspect they tossed that e-mail away because they responded to my website improvement suggestions and some other basic info, but nothing about how they operate behind the scenes.

I've gotten my ROI from them in terms of USD value. In terms of BTC, I'm keeping track of that on a sheet. They're a bit more than halfway repaid in my book. It'll take a couple more months until it's repaid in full. After that, any extra BTC I get from them is fine by me, plus any extra GH I get from referrals. I'm moving onto Bitcoin Cloud Services, and checking them out. The operator seems more transparent and more responsive than PBMining's operators, so we'll see how that ball rolls. Their pricing is very similar to PBMining with higher minimum GH orders. We'll see how this goes.