Is BitClub a Ponzi Scheme?
NO! Very important to understand that they DO NOT guarantee a mining share will have a set return. In fact, you will never hear them make any claims about how much you will earn from having a share in their mining pool because the truth is they don't know. Bitcoin mining is very complex and with the difficulty level constantly moving up every 10 days and new hashing power always entering the space there is no way anyone can predict accurately an ROI. Especially with their business model that requires re-purchases or more simply daily maintenance fees.
NOTE: If you find a company offering you a set return (especially if they claim to be Cloud Mining and offer 100% or more) there is a high probability they are a Ponzi scheme. Some Cloud Miners are actually backed by real hardware but their power is virtual and therefore very hard to track. In fact, the sad reality is you will never know if a could mining company is actually mining, so it is recommended that you steer clear unless they are very transparent. BitClub is NOT a Cloud Mining company, everything they have can be verified!