According to Bloomberg, the computer trading error that cost Knight Capital, the US market maker $440m (£282m) (see IF 9th Auguts 2012) can be blamed on disused software.
(On August 1, the dormant system was accidentally reactivated when a new program was installed. As a result stock trades were multiplied by 1,000, causing wild swings in the share prices of almost 150 companies. So, now we know. The big question is, what are we going to do about it?)