What exactly do you mean by fractional reserve mining? Do you mean to imply that they sell 3 TH/s for every 1 TH/s of mining equipment they actually own? If this was the case then what would the point of this be? I would think they would either have mining equipment that backs up all of their mining contracts sold or have no mining equipment at all; I think having only a fraction of mining equipment to backup the mining contracts would make very little sense and your claim that this is what they are doing only degrades your credibility
I am not the only one who suspects this is going on :
https://www.cryptocoinsnews.com/gavin-andresen-suspects-ponzi-schemes-bitcoin-cloud-mining/I hate to be so explicit for something that is obvious but here it goes:
A cloud mining company has 3 options(and I suspect most are taking option 1 and 2 ) since those are the most profitable options
1) 100% Ponzi Operation, easy to setup and operate and thus easy to undercut all the other companies as. All they need is a few shill accounts, a cheap website, and an affiliate program and they can pay affiliates and and take a cut before payouts. Since cloud mining payouts rarely have a 100% ROI and are over multiple months they even have more of a buffer even if their growth slows before being forced to shutdown.
Certain cloud mining operations have already been exposed and shutdown doing exactly this.
2) fractional reserve mining - This group are either legit companies which started with 100% hashing to back up their clients but started padding their hashes to increase profitability or companies who occasionally make a large purchase to lend credibility to their claims of having 100% hashing but never intended to have 100% hashing power to back up their claims. Some of these companies are interested in profiting directly off of mining and selling bitcoins themselves but will certainly never turn away a contract even if they don't have the hashing power to back up their claims because they usually have more expensive contracts and thus are unlikely to ever have to payout more than they take in so might as well grab free money. These companies don't mind mining for its own profitability sake but they cannot always secure fair price from the ASIC manufacturers.
3) cloud mining with 100% hashing backing up what they sell
Since most contracts rarely have a ROI simply taking the cash and slowly giving back a slightly less amount of cash is far more profitable than buying ASIC's where they have to install them, maintain them, pay for electrical costs, and have all sorts of liabilities.
If a company isn't doing either 1 or 2 than why aren't they stepping forward and provided better evidence. Few have even offered and this would be a chance for them to instantly gain the credibility of the community and garner more contracts.