The furor is over revelations that Barclays, the Royal Bank of Scotland, and other banks were monkeying with at least $10 trillion in loans (The Wall Street Journal is calculating that that LIBOR affects $800 trillion worth of contracts).
The banks gamed LIBOR for two semi-overlapping reasons. As noted here last week, there were instances of Barclays traders badgering the LIBOR submitters to "push down" rates in order to fatten their immediate bottom lines, depending on what they were trading or holding that day. They also apparently rigged LIBOR downward in order to produce a general appearance of better health, essentially tweaking their credit scores a few ticks upward.
Most intriguingly, or perhaps disturbingly, there were revelations last week that Bank of England deputy Governor Paul Tucker had a conversation with Diamond at the peak of the crisis in 2008. The conversation reportedly left Diamond, and subsequently his traders, with the impression that the bank had carte blanche to rig LIBOR downward in order to help allay spiraling public fears about the banks’ poor financial health.