"There are two kinds of bankers to fear. The first is incompetent and runs a big bank. This includes such people as Chuck Prince (formerly of Citigroup) and Ken Lewis (Bank of America). These people run their banks onto the rocks – and end up costing the taxpayer a great deal of money. But, on the other hand, you can see them coming and, if we ever get the politics of bank regulation straightened out again, work hard to contain the problems they present.
The second type of banker is much more dangerous. This person understands how to control risk within a massive organization, manage political relationships across the political spectrum, and generate the right kind of public relations. When all is said and done, this banker runs a big bank and – here’s the danger – makes it even bigger.
Jamie Dimon is by far the most dangerous American banker of this or any other recent generation."
It's a bit odd to vilify Dimon for not totally screwing things up like his competitors did, but Johnson's point seems to be that Dimon's success (and yes, I know that Dimon's JPMorgan has benefited vastly from the Government's interventions) makes his bank bigger, more powerful, Too-Bigger-Too-Fail, and ultimately more dangerous on a systemic level.