I don't really understand the referral concept.
Since they're sending you their BTCs, why do you need to trust them?
The same way you need to trust the bank you get your mortgage from.
No, it's more like the bank needing to trust you for accepting money you deposit with them. They're taking your money and paying you interest on it in the same way as pirateat40 is...the depositor is taking the risk that the bank pays interest and doesn't run off with the capital.
In your scenario, you're the one taking the loan, so the bank needs to trust you, not the other way around, and the more they trust you, the more they'll lend you / lower your interest rate.
I don't think he want to have to deal with a lot of movement in and out.
Yeah that's fair enough, it's just that referrals in the guise of security doesn't make much sense: "this model allows me to limit the new accounts from unknown, new or untrustworthy members."
I understand not wanting to deal with 10000 withdrawals/deposits all the time, and pirateat40 has said as much before, but a referral system will create exactly that. The only thing faster than wildfire is word of mouth.