Bailing out Too-Big-To-Fail banks which privatise profits and socialise losses on increasingly abstract / difficult to understand financial instruments springs to mind.
If you're talking about the recent bank failures, that was in fact covered by other banks, no? It was not paid for by tax payers.
While the recent losses were in big part because of bonds and currency rate risk, so not a particularly abstract or difficult to understand instrument.
Not that being hard to understand is a bad thing. Something can be complex and still valuable.
