Fannie Mae, the beleaguered American mortgage shambles, has just appointed David Johnson as its new CFO.

Curiously, it appointed controller David Hisey to that role three months ago, with no mention that we can see to the effect that his appointment was 'interim'. Hisey took over from Stephen Swad, who took on the role in mid-2007, and so was the one with the front-row seat when it all went pear-shaped, as our recent feature reported.

Three CFOs in just over a year is pretty good going. But of course it's even worse than that. It was as recently as January 2006 that Robert Blakely was appointed CFO, and he, in turn, took over from an interim CFO, Rob Levin, who took on the job at the end of 2004 after an accounting scandal that forced the group to withdraw and restate its accounts for 2001-2004.

So, including the guy that Levin took over from, that makes six CFOs in barely four years.

If you fancy a crack at the job yourself, you may get another chance before long, the way things are going...