I generally take credit with great caution. Here you are offered interest, and for this you must transfer your coins to someone and lose complete control over them? This may well be a classic financial pyramid, only with the participation of the crypto currency. Where is the guarantee that if the volumes of the listed coins from any of these enterprises turn out to be very large, this enterprise will not cease to exist and will not run away with digital coins received from different people? After all, it will be very difficult for you to apply to protect your interests. After all, everything is anonymous and in the territory of different states and jurisdictions. In this case, you will be practically defenseless and scammers can count on this. Therefore, I do not recommend taking such risks, even regardless of the fact that these companies are still carrying out oral agreements and transferring you coins as interest. All this can be up to a certain time.