Cloudhashing isn't an outright scam as in they probably intended to fulfil they contracts they sold. However both the way they marketed it and how they are dealing with their customers is definitely shady.
They made a big play about being a UK registered company, that implies that you are safe because they are operating under UK consumer law.
False advertising:
The returns advertised were never going to be achieved.
Breach of contract:
The July contract holders were given just 20% hashing power late in July after being sold 100% starting July 4th. They were told that compensation would be announced after achieving full hash power. When that was announced and was nowhere near what was lost. They then refused to refund saying it was too late. This is a lie as they failed to deliver what they sold, customers are entitiled to refunds by law.
September contracts were simply switched to October contracts with no compensation at all, so with the ~100% difficulty increase, they received about half of what they paid for. Again a breach of contract and they refuse to refund.
Distance selling regulation:
New customers signing up now are entitled to change their mind and get a full refund within 7 days of purchase. Cloudhashing deals with this by ignoring them until the 7 days is up.