I especially liked his discussion of “front book, back book“. Banks and insurers accumulate a long-term book of assets. These generate a predictable stream of income (interest and premiums). Unfortunately, this “back book” exposes them to unexpected losses. As a result, financial firms need a lot of capital.
The business model of Software-as-a-Service (SaaS) companies is also based on a back book. However, unlike banks, their portfolio of subscribers does not require a lot of capital.
In the same newletter, Rubinstein discusses the possibility of bank M&A funded by badwill, as I suggested earlier.