If there has been a lesson to learn here on this forum over the past 2 weeks or so - maybe it's been that databases of 3 billion webpages can't get major algorithm calculation and filter updates, and then get reindexed or reanythinged, with the 'flip of a switch'.
It obviously takes weeks and weeks of reprogramming, testing and replication to do this stuff on a distributed database over 10,000 machines in 9 datacentres. And no - most companies (not just search engines) can't afford to 'double up' their hardware platforms so that they can test things 100% 'behind closed doors' - then 'flip a switch' and go live with a new product.
So - my advice is to learn from this Dominic episode, and start planning for a different future commercial reality - and start to focus your energy on your own 'disaster recovery plan'. That way - if/when Yahoo moves to Inktomi - or anything else happens - you'll be ready with a 'Plan B'.