What about stability? If the serps move around like crazy, the users wont find their old pages they used to find.
Apparently the people at Google don't understand the point you're making, because I've certainly had people I've talked to about Google complain about it, but the people at G don't seem to have any clue how many people don't like the 'ever changing' results and the personalization... It's like they look at their search numbers and think 'Wow, we're doing so much better!' and don't ever stop to think their search numbers are increasing because people can't find what they saw earlier or yesterday and don't like it.
When I explained to one friend of mine about the personalization they said 'Now a bunch of things make sense... I wasn't ever going to do it, but I might try Bing.'
[edited by: TheMadScientist at 1:38 pm (utc) on May 4, 2010]