I am the founder of arbX (http://arbx.co)
We run a Professional Arbitrage Trading with over 2,000 BTC in funds under management.
These funds include an arbitrage fund - Proof of stake visible on the blockchain and summarized here https://www.coinprism.info/asset/AQKbkUkQjKLe7ru44MhgkU8UnnrDUSEqjn/owners
And now a Short Term fund for participants with 10BTC and over - https://www.coinprism.info/asset/AVM7oaYu47qSxnLmWy6fFkVQ6YijCdp4Jk/owners
Despite this we still find ourselves with opportunities that make online borrowing for opportunities worthwhile and GetLine & POP have become our preferred and soon to be only platforms for lending for these opportunities.