I believe it does. I can say this because in case of some SERPS that i track for a week, 3 days out of 7, i show on the first page and during the later part of the week move to second page, in some cases it also happens fortnightly. Has this being happening with others also?
Just look at the different datacenters for your answer. They always have different algos in place either for testing or development.
I think Google tweaks the algorithm based on the query competitiveness. That's why I don't believe all the SEO tests using words like alkdjfaslkdjasljk.
I noticed a bump in a highly competitve keyword search this morning (7/21) I think these changes occur often and unpredictably.
Many times I've done the same exact query a few minutes apart and gotten different ordering of the top 10 SERPS. This tells me that the search algo factors in some noise (randomness) when it needs to order results that are closely ranked. I'm sure you guys have experienced the same... LC
i think the notion of them adding randomness (even if not on the fly) is a very good point and i was thinking the same thing earlier this week. what better way to keep us all dumbfounded and guessing? add a complete random variable in.
I believe it said it does somewhere on the site. Can't find the link right now, but its somewhere I believe.
I think google ranks sites based on some weighted rule .. for eg: w1 * f1 + w2 * f2 + w3 * f3 .... + wn * fn where fn is the factor and wn is the weight. I think google keeps changing the weights from time to time to tune the results. There has been a major weight change in the past 24 hrs ... the factors fn are pre-calculated but the weights keep changing. For eg one factor is the keyword density , another is the famous google pagerank.. I think in the last 24 hrs the weight for PR has been increased by a very big number !! I am sure you guys must have seen the change too !! Just my opinion.