1. That Lehman Brothers and AIG were not universal banks that could be considered for separation, and yet they caused systemic concerns
2. That is was not the global systemically important financial institutions (GSIFI) banks that failed during the crisis; it was the specialised mortgage banks involved in the real estate boom busts in the USA, the UK, Ireland and Spain that mainly failed.
3. The separating core deposit banking will force investment banks into more wholesale funding, which the distance-to-default (DTD) model results suggest is a riskier business model feature
4. That it is legally too complex to separated assets and liabilities while meeting all of the tax and corporate laws of the country concerned.
5. That separation with full ring fencing of all subsidiaries is essentially Glass-Steagall, so why bother with non operating holding companies (NOHC)?
Lehman Brothers: http://en.wikipedia.org/wiki/Lehman_Brothers
Global systemically important financial institutions GSIFI banks: http://en.wikipedia.org/wiki/GSIFI
Distance-to-default (DTD) model : http://www.oecd.org/finance/BanksBusinessModels.pdf
Glass–Steagall Legislation: http://en.wikipedia.org/wiki/Glass–Steagall_Legislation
Non operating holding companies (NOHC): http://wiki.answers.com/Q/What_is_non_operating_holding_company#slide1