A surprisingly small number seem to have joined the army though. A recent report in the New York Times suggested US military academies are suddenly getting lots of applications. The Royal Military Academy at Sandhurst was unable to say whether it's also benefitting, but it did quantify the number of ex-bankers who joined last year: two.
We weren't allowed to talk to them, so can't enlighten you on their motivation.
However, time spent in the office corps has traditionally been seen as a prelude to career as a corporate broker or corporate financier, and may prove a cost effective way of riding out the downturn.
A spokesperson for Sandhurst said would-be army officers need to be aged 18 to 28 and to have at least two A levels. Training lasts for 44 weeks and payment during training is 16k for non-graduates and 24k for graduates. While this isn't great compared to investment banking, it doesn't look too bad compared to the 40k you'll spend in tuition costs alone on doing an MBA. And officer-hiring is actually up - according to The Times two hundred new additional officers are being hired for the army, navy and RAF this year.