I think Bitcoin is the safe investment which could give you automatic returns for simply holding it. Also many things to be considered while participating in such bonds. One of it is the hard-forks.

Say after lending the coin, the chain was hardforked similar to BCH. Logically the lender should be in control of the new generated forked coin. But as he has transferred it to the borrower before the fork happened, borrower would be in control of the new coins.
There may be many other things to be considered.
So personally I try to stay away from such scheme without analyzing in depth or until trusted people like Andreas Antonopoulos claims it to be good.
Good luck to all who are planning to invest in these schemes. Do good research and due diligence before investing your hard earned money. Cheers!!!