In acquiring Autonomy, HP basically admitted that it set fire to about $9B. This would be bad enough if it wasn't for the fact that this is not the first, not the second, but the third time in a year that HP has admitted that a company it spent more than a billion dollars acquiring was worth far less than it paid for it. In 2008, HP bought Electronic Data Systems for $13.9B and wrote that down by $9.8B last quarter. In 2010 the company bought Palm for over $1B and shortly thereafter shut the operations down. In all the sum of these three write-downs is worth almost as much as HP's current market cap!
Worst of all, the carnage from the Mark Hurd/Leo Apotheker era still might not even be done yet. In 2010 (while the company was being led by an interim CEO if memory serves) HP made three other multi-billion dollar acquisitions at big revenue multiples. 3COM, 3PAR and Arcsight could each be a candidate for billion dollar write-downs as well.