Roughly nine months ago, Bitcoin Foundation Chief Scientist Gavin Andresen made a rather interesting comment on Reddit in which he claimed, “I suspect many [cloud mining companies] will turn out to be Ponzi schemes.”
https://bitcoinmagazine.com/20702/exclusive-possible-500000-bitcoin-cloud-mining-ponzi-scheme-uncovered/
Sooner or later they will turn out to be a ponzi scheme.
The logically is when the diff always increased why they want to rent their equipment, they will get low profit(if they really rent their equipment) and turn into ponzi scheme is possible.