I am seeing major reports on a Yahoo Search update at WebmasterWorld right now. The timing makes sense, it is just about one month from the August 2008 Yahoo update. I would not be surprised if we see a post today or tomorrow at the Yahoo Search Blog announcing the update, which they call the "weather report," based Danny's request but I gave Tim Mayer credit.
This Yahoo Search update is fairly major. Senior member, BillyS, said:
Our traffic is up around 30% on Yahoo starting some time Friday night. Is anyone else seeing this too?
I've always been under the impression that Yahoo gives a lot of weight to a domain's age. We might just be hitting one of those threshold values - our site is nearly 5 years old now.
Others notice up to 50% more traffic from Yahoo.
Forum discussion at WebmasterWorld.
Update: Yahoo announced the update, a day later, as expected.