If you have no product, PR is all you can do.
of course it's a scam. 99% of all cloudminers are nothing but hot air

Hashflare is paid me 1,5 years so far so I'm good with them.
HashOcean was paying almost two years, and it was Ponzi scheme. Time of paying doesn't mean that service is legit. You have to investigate who is staying behind, where is farm - and of course if this farm is real. Usually farm is just virtual.. That's are classic scam services.
Bernard Madoff's ponzi lasted half a century - if there is something ponzis are kown for that its longitude. Most ppl see someone as familiar the third time they met and talked. This may be an inherent weakness in human nature.
Yep, Madoff was running his Ponzi 48 yeras (?) .. Even the special commissions that have investigated eight times and found no signs of a scam.
So I can not say that it is easy to recognize a scam. However, we should think a bit before we give someone our money. If something looks too good, it probably is a scam - espeially in cryptocurrency world.