When I look at any investment structure, I ask, who has the most to gain and who has the least at risk? Does btcpop.co supplement the collateral so all loans are 100% refundable? If not, you force the lender to take extra risk at the cost to the profit of the company. I don't like these systems at all, especially if they don't have multisig to lock in contractual agreements. It's too early to do loans the proper way. Hence, I recommend people to not lend, but keep making money just buying and holding btc. But lending... You give up your keys, you give up your btc.