Well the thing about "verifiability" proving something is that not everyone agrees on what exactly would meet this standard.
I would say that it is generally not possible to prove beyond most naysayer's doubts that any cloud company has the physical hardware. Pictures can be faked, the same with invoices, and allowing people to physically see the equipment poses a security risk.
The answer to proving that a company owns actual equipment is to show them the mining address. The issue here is that even this can be faked. A company could rent mining capacity for a period of weeks or months when the term of a mining contract is years. Another way to fake a mining address would be to claim they are mining at a pool (like many smaller cloud mining companies probably are - when they are actually operating in a legal way) that doubles as an exchange (cex.io). The company could launder proceeds from their contract sales either through a mixer or through a large exchange like bitstamp, then deposit the proceeds into cex (the sales proceeds would not go directly to cex in order to make it difficult to draw the connection). Now the company is able to send payments to their customers from an address that can be easily traced to mining proceeds.
I would say that it is generally not possible to prove beyond most naysayer's doubts that any cloud company has the physical hardware. Pictures can be faked, the same with invoices, and allowing people to physically see the equipment poses a security risk.
The answer to proving that a company owns actual equipment is to show them the mining address. The issue here is that even this can be faked. A company could rent mining capacity for a period of weeks or months when the term of a mining contract is years. Another way to fake a mining address would be to claim they are mining at a pool (like many smaller cloud mining companies probably are - when they are actually operating in a legal way) that doubles as an exchange (cex.io). The company could launder proceeds from their contract sales either through a mixer or through a large exchange like bitstamp, then deposit the proceeds into cex (the sales proceeds would not go directly to cex in order to make it difficult to draw the connection). Now the company is able to send payments to their customers from an address that can be easily traced to mining proceeds.
I agree, thats why I said its not impossible, just a whole lot more difficult and expensive. But in order to score full marks on my criteria, you also need an asic vendor to vouch for you and there should be no doubt about the identity of the people behind the company. Not many scammers like to expose themselves to prosecution.
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While I agree that as of today it does not make sense for a cloud ponzi to do much more then their cookie cutter approach, I think that the market will get "smarter" and people will watch out for these kinds of red flags
I wouldnt hold my breath. I lost count of the number of ponzi's Ive seen come and go over the past years, and if anything, they are getting more transparent (as in, more obvious to be a ponzi), not less.
Hard to know in advance, not sure if PBmining is amongst those suspiciously low charging anymore @ 0.0014btc/GH currently.
I find most cloud mining sites suspicious in one way or another. Not sure if I'd call some of those legit sites not being scams. If ROI was never even possible (because of maintenance fees and estimated difficulty increase) aren't those sites scams also? and the way many market themselves is like difficulty will never increase or even use old stats from mining months ago to deceive new customers. The whole cloud mining business seems a very dishonest one and hard to know where to invest. So judging from what everyone says it seems most legit ones will never ROI and the ones who will are all possible ponzi's 
