At the top end of the game I imagine people have a LOT of space money kicking about and no real time to use it - making them demotivated and play the game less often. This is why I think we should be able to compete directly with the bank by giving out loans to smaller companies based on the base rate of interest and the supply and demand for loans/money. This cost of production (base rate of interest) will mean you (the moderators) can control the effect lending has on the market, but it will also encourage the highest "level" business owners to play more to control their lending on a higher scale, and smaller companies to grow faster because of cheaper finance.
Also we will never have the problem of the sub-prime crisis because nobody risks going into negative equity! 