I am an investor in the Felix fund mentioned in the business week article. All they did is buy up several million dollars of Facebook stock from original shareholders, put it into a simple LLC, and then sell shares of that LLC. Investors pay an upfront transaction fee on the investment, a minimal operational cost, and then a fee on the backend if there is a liquidation event but only after the investor gets 100% of their investment back.
This is very similar to how traditional VC funds are structured and the only reason this is getting press is because it is another story about Facebook.
These funds actually do a service for the original Facebook shareholders because it allows them to take some cash off the table, rather than waiting for the IPO.