Felix Salmon, pivoting off this somewhat obscure post, makes a great point:  

Essentially, we are not living in a world where investment prowess is repaid, and the fate of the private-sector participants in Geithner's public-private partnerships is pretty much out of their hands. Either all of these assets are going to appreciate in value, or all of them are going to decline in value. And that's largely a function of what happens to international financial markets and to the global economy as a whole. The potential buyers of these assets can do all the homework they like, trying to bid on slightly better assets rather than slightly worse ones, but the big risks -- to both the downside and the upside -- are systemic.

In other words, the private participants in the Treasury plan aren't really adding value, they're just gambling that things are more likely to get better than they are to get worse. For this we need to pay them much more of the profits than their share of the total investment?

Eventually, if things get better, then this kind of plan might make sense: correlations will come back down from 1, where they are presently, and private investors will be able to play a useful role in separating the wheat from the chaff when it comes to those legacy assets. For the time being, however, the days for such sifting remain far in the future. And it's not at all clear why it pays to bring private investors in at this stage.

Update: One of Salmon's commenters also makes a good point, about whether it's wise for the banks to even put their assets on the auction block:

Isn't the big hurdle getting the banks to offer up their assets to the auction process by FDIC? Once they do that, whether they accept the bid or not, it seems hard to imagine they would be able to value the assets very much above the highest bid offered. For example, if the assets are valued on their books at 50% of face value, they offer them in the auction process and the highest bid is 30%, I would think it would require a little chutzpah to decline the bid and go back to valuing these assets significantly above what has been shown as a market price.

Right. The whole point of the Geithner plan is to create a market to set prices--the theory being that the lack of a functioning market has led to irrationally low prices for the toxic assets. But what if you set up the market and the prices are still so low they leave the banks insolvent? Even if the banks don't sell, you've not only revealed what a lot of people believe to be true, you've also stamped that belief with your imprimatur.

--Noam Scheiber