I can see u r affectionate towards BitFury and angry at PB Mining.
Angry is the wrong word. I just don't support their shady business model.
Moreover, one does not need to continue maintaining the same address to show they are mining. They can simply rent an address for a few days and show it as 'proof' for months.
That's not how it works. You cannot prove a company is currently mining by providing an address that is not currently mining.
Look at
https://www.antpool.com/poolStats.htm . Every day new blocks are found and signed with "mined by antpool".
Regarding 'unknown entity', its a vague concept in bitcoin world. What will u do if CEX goes out of business tomorrow ? What u have been able to do to MK after the Mt. Gox fiasco. Everyone is always at risk and the concept of vague certainty should be abolished. While choosing the service I'll simply go through the rate chart and this is what I have now...
1.
https://cex.io/ => 0.00268387 BTC/GHS
2.
http://pbmining.com/ => 0.0021 BTC/GHS
3.
http://www.cloudmining.website/ => 0.001 BTC/GHS
So basically what you're saying is that because there are so many scams, you might as well invest in the best priced offering regardless of how sketchy/untrustworthy?
Why would you willingly invest in something that has a 50/50 chance of being a ponzi? That's like playing roulette and betting on red, but instead of doubling your money if you win, you will maybe earn 10% profit after 6 months.
Just go to a casino where the risk is the same but the reward is 10 times greater.