We advertise with Bing and receive a bit of traffic from them. Then suddenly yesterday, out of the blue, the ppc traffic surged. It lasted about 24 hours and then petered out. Our logs show it all came from Yahoo search and one particular keyword search. It also showed that the keyword phrase was exactly the same three words, all capialized, for each search.
If it were content network traffic it would make sense. But what causes thousands of people to suddenly search on Yahoo for one particular, identical phrase?