One of the noteworthy issues is that the BM context is not analogous to the real world. In real life, banks can get quite powerful because a lot of people NEED/want to use its services. It's safer to deposit your gold at the bank than in your house. This allows the banks to accumulate quite a lot of capital, with which they can grant loans or finance projects. This is not the case in BM. The game already provides banks. At any of the realm's cities, a noble can exchange his gold for bonds, and nothing can touch those bonds. Wealth isn't even taxed anymore as it used to be. And with but minor adjustments and costs, nobles can walk around with tens of thousands of gold on hand, and not seriously risk losing it. As trading is now done in bonds, the banking has already become international. Furthermore, depositing in a bank is safe. Giving anything to anyone in BM is risky. What if the guy goes on vacation for a few weeks and puts his character in cold storage? What if he loses interestest in BM? Or something happens to him IRL? If the player dies, you can't expect his successors to go log into his BM so that they may continue to safeguard the funds to entrusted in his character. In RL banking, something happening to someone at the bank doesn't jeopordize your savings.
I, for one, have seen many players come and go. Often in untimely manners. I would therefore be quite reluctant to give any significant funds to anyone unless I really didn't care to see them back. I also can't say that I've never had so much excess gold that I didn't know what to do with it... The family gold cap is quite high, and that allows you to invest in (your) region, so it's really like a bank too.
