Dodgy accounting
If HP paid $11.7bn, but wrote off $8bn on Autonomy, and have subsequently lost the Autonomy founders, as well as (on recent reports) the UK sales force, then presumably they'll be happy to let it go at book value?
Of course, if they want more, then that implies that the write down was contrived. Do we think Meg will report herself to the SEC over accounting irregularities?