This brief post by Salmon reminds me that TBTF is here to stay, despite numerous calls to break the big banks up. Given that, what should we do? The so-called "tax" in the linked article would be a partial fix, but I don't think its enough. I would like to see a multi-dimensional insurance fee (or tax if you prefer) based on risk, size, and leverage. Some qualitative measures could be thrown in as well - stability of funding (deposits vs. brokered deposits vs. credit markets vs. whatever), strength of internal risk analysis, corporate structure, over-concentration or over-diversification, and more I haven't thought of. The idea of making the fees counter-cyclical should be implemented as well.
Of course, such a wonderfully precise system is about as likely as breaking up the big banks - both are blocked by the fact that the banks "own" the Senate (per Dick Durbin). But I can still dream, eh?