Punitive expedition or justified measure?

While some American banks are thriving again (see, for example, here), President Obama proposed to levy a 0.15% tax on the liabilities of the largest financial institutions, with the aim to “recover every single dime the American people are owed”. The proposal has drawn mixed reactions (here) and Congress’ approval cannot be taken for granted. The fundamental question is about the real effectiveness of such a fee: does it represent a little step toward a more equitable economy, or is it only a populist initiative with marginal or counterproductive effects on the economy?

Update: a proposal and commend from D. Diamond and A. Kashyap.