There is a very non-factual rumor, with very little current backing, that when Google does search updates, it first updates the mobile phone index, the one that iPhone, Android and Palm OS uses, and then the main desktop index. I don't think they have different indexes for mobile phones to access versus desktops to access - but it is possible they show a fresher Google data center to mobile users or test things out first on mobile users.
Again, this is all early speculation, that even if true, could have happened once and could never happen again. Here is the first post from WebmasterWorld with this discussion:
Have any of you guys monitored your keywords via your mobile phone (I'm using the Droid phone) and noticed a difference in the SERPS between you cell phone and your home computer?
Since beginning of January, whenever a ranking change would occur, I would notice it first on my droid phone (after being logged out) and then a day or two later, in the SERPS when the same query was run on my home computer.
Is there any correlation between the two or am I just experiencing an anomaly?
Senior member, whitenight, said he was considering the same thing but didn't want to say anything yet. While administrator, Roger, found the theory to be "interesting."
Forum discussion at WebmasterWorld.