I was thinking of solutions, and the easiest would be to simply disallow large deposits. But, there are not that many people interested in trusting their coins to someone online, and those who are tend to deposit large amounts -- that solution cuts us off to a lot of funds we could be profiting off of by reinvesting in the community, likely to the extent that accepting deposits is more a hassle than worth.
A similarly easy, and much more effective solution is to limit withdrawal rate per person. For example you could say withdrawals are limited to 25 BTC per day. So someone who wants to deposit 500 BTC will be accepted with open arms, but will do so with the understanding that it may take up to 20 days to withdraw everything.
Instead - what if we we listed bonds or 'fund shares' through something like GLBSE?
Also a good idea. But its main advantage, the liquidity provided by GLBSE, might only be realized when GLBSE gains in popularity (which might be brought about by GLBSE 2.0), and with relatively large lenders. Otherwise, I can see how someone wanting to exit the investment by selling on GLBSE would suffer significant slippage. (Bidding on one's own bonds could mitigate this, but is not easier than having reserves from which to withdraw CDs.)
Not a fan. It's much easier to trust one's honesty in honoring the terms of a bond, than his competence in running a successful lending business.