The Compulsive Theorist has written a truly excellent post on bank bailouts (ht Mark Thoma). I'll excerpt a bit below, but do read the whole thing:

I sympathize with the point of view which says that the political window of opportunity is narrow and the need for action urgent, so let's accept the bailout plan for now, and deal with... wider issues later on. But the very fact that political momentum is limited means that if these wider changes are to be brought about, the process has to begin in earnest at once. Does anyone seriously believe that in a years time, if following massive government support the banks are stable — or can be made to appear stable — there will be any political will to break up very large institutions, or any real change to underlying norms in the financial sector?

However, absent these deeper changes, it is entirely possible that we will see a replay of the crisis — but on a larger scale — in a few years time. Naturally, one cannot say with certainty that such a cataclysm (and if it were much larger than the current crisis, it really would be a cataclysm) will occur. But if it does, the resulting costs will be huge. Martin Wolf has written persuasively about the costs of major economic dislocation. Net of unemployment, political instability and even wars, the human costs of a sequel could dwarf even the current crisis. Then, the choice in the present between the "bailout" and "restructuring" plans hinges on whether expected cost (in the broadest sense), conditioned on the "bailout" strategy is higher than expected cost conditioned on "restructuring". One could formalize this argument as a decision problem, but it comes down to a judgement call on the relative probability of such a cataclysm under the two strategies and the magnitude of the dislocation. My feeling, admittedly subjective, is that the gloomy cataclysm scenario is substantially more likely under the "bailout" than "restructuring", and that the costs would be immense.

This case can be put very simply: if we do not use current political momentum to fundamentally reform a system which has shown itself to be unstable and even dangerous, a second opportunity may come at a very high price. And this is not a gamble I wish to see our leaders make.